Waves EB
Waves EB
9702/22/F/M/23 Q5
5 1.(a) A microphone and cathode-ray oscilloscope (CRO) are used to analyse a sound wave of
        frequency 5000 Hz. The trace that is displayed on the screen of the CRO is shown in Fig. 5.1.
1.0 cm
1.0 cm
Fig. 5.1
         (ii)   The intensity of the sound detected by the microphone is now increased from its initial
                value of I to a new value of 3I. The frequency of the sound is unchanged. Assume that
                the amplitude of the trace on the CRO screen is proportional to the amplitude of the
                sound wave.
On Fig. 5.1, sketch the new trace shown on the screen of the CRO. [3]
(b) An arrangement for demonstrating interference using light is shown in Fig. 5.2.
3.6 × 10–4 m P
         The wavelength of the light from the laser is 630 nm. The light is incident normally on the
         double slit. The separation of the two slits is 3.6 × 10–4 m. The perpendicular distance between
         the double slit and the screen is D.
         Coherent light waves from the slits form an interference pattern of bright and dark fringes on
         the screen. The distance between the centres of two adjacent bright fringes is 4.0 × 10–3 m.
         The central bright fringe is formed at point P.
(i) Explain why a bright fringe is produced by the waves meeting at point P.
...........................................................................................................................................
..................................................................................................................................... [1]
D = ...................................................... m [3]
    (c) The wavelength λ of the light in (b) is now varied. This causes a variation in the distance x
        between the centres of two adjacent bright fringes on the screen. The distance D and the
        separation of the two slits are unchanged.
         On Fig. 5.3, sketch a graph to show the variation of x with λ from λ = 400 nm to λ = 700 nm.
         Numerical values of x are not required.
                                           0
                                           400                                                     700
                                                                                  λ / nm
                                                                   Fig. 5.3
                                                                                                                                                       [1]
[Total: 10]
         State the other condition that must be fulfilled by the two waves in order for them to produce
         the stationary wave.
............................................................................................................................................. [1]
    (b) A stationary wave is formed on a string that is stretched between two fixed points A and B.
        Fig. 5.1 shows the string at time t = 0 when each point is at its maximum displacement.
A B
Fig. 5.1
(i) On Fig. 5.1, sketch a solid line to show the position of the string:
    (c) A beam of vertically polarised light of intensity I0 is incident normally on a polarising filter that
        has its transmission axis at 30° to the vertical, as shown in Fig. 5.2.
       vertically polarised
       incident light                        30°             transmitted                                           transmitted
       beam,                                                 beam,                                                 beam,
       intensity I0                                          intensity I1                                          intensity I2
Fig. 5.2
         The transmitted light from the first polarising filter has intensity I1. This light is then incident
         normally on a second polarising filter that has its transmission axis at 90° to the vertical. The
         transmitted light from the second filter has intensity I2.
         Calculate:
                            I1
          (i)   the ratio
                            I0
                                                                           I1
                                                                              = ......................................................... [2]
                                                                           I0
                            I2
         (ii)   the ratio      .
                            I0
                                                                           I2
                                                                              = ......................................................... [2]
                                                                           I0
                                                                                                                              [Total: 10]
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [1]
(ii) State why light waves can be plane polarised but sound waves cannot.
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [1]
    (b) Two polarising filters A and B are positioned so that their planes are parallel to each other and
        perpendicular to a central axis line XY, as shown in Fig. 4.1.
                                             filter                                               filter
                                                A                                                    B
                                                                                                                     direction of
                                                                                                                       rotation
                                                                   I0
          X                                                                                                                            Y
                unpolarised
                   light
                                       vertical                                             horizontal
                                  transmission axis                                     transmission axis
Fig. 4.1
The transmission axis of filter A is vertical and the transmission axis of filter B is horizontal.
         Unpolarised light of a single frequency is directed along the line XY from a source positioned
         at X. The light emerging from filter A is vertically plane polarised and has intensity I0.
         Filter B is rotated from its starting position about the line XY, as shown in Fig. 4.1.
                                                                             1
         After rotation, the intensity of the light emerging from filter B is I0.
                                                                             4
         Calculate the angle of rotation of filter B from its starting position.
    (c) A microwave of intensity I0 and amplitude A0 meets another microwave of the same frequency
                        1
        and of intensity I0 travelling in the opposite direction. Both microwaves are vertically plane
                        4
        polarised and superpose where they meet.
          (i)   Explain, without calculation, why these two waves cannot form a stationary wave with
                zero amplitude at its nodes.
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
(ii) Determine, in terms of A0, the maximum amplitude of the wave formed.
[Total: 10]
A 5.5 cm
magnifying glass
         The magnifying glass is circular in cross‑section with a radius of 5.5 cm. The intensity of the
         light from the Sun incident on the magnifying glass is 1.3 kW m–2.
Assume that all of the light incident on the magnifying glass is transmitted through it.
(i) Calculate the power of the light from the Sun incident on the magnifying glass.
(b) A laser emits a beam of electromagnetic waves of frequency 3.7 × 1015 Hz in a vacuum.
[2]
(ii) State the region of the electromagnetic spectrum to which these waves belong.
..................................................................................................................................... [1]
        (iii)   The beam from the laser now passes through a diffraction grating with 2400 lines per
                millimetre. A detector sensitive to the waves emitted by the laser is moved through an
                arc of 180° in order to detect the maxima produced by the waves passing through the
                grating, as shown in Fig. 5.2.
detector
                                                     diffraction grating
          laser
                                           beam from
                                           laser                                                                 detector moves
                                                                                                                 along this line
Fig. 5.2
               Calculate the number of maxima detected as the detector moves through 180° along the
               line shown in Fig. 5.2. Show your working.
        (iv)   The laser is now replaced with one that emits electromagnetic waves with a wavelength
               of 300 nm.
               Explain, without calculation, what happens to the number of maxima now detected.
               Assume that the detector is also sensitive to this wavelength of electromagnetic waves.
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
[Total: 12]
5 5. Light from a laser is used to produce an interference pattern on a screen, as shown in Fig. 5.1.
    The light of wavelength 660 nm is incident normally on two slits that have a separation of 0.44 mm.
    The double slit is parallel to the screen. The perpendicular distance between the double slit and
    the screen is 1.8 m.
    The central bright fringe on the screen is formed at point O. The next dark fringe below point O
    is formed at point P. The next bright fringe and the next dark fringe below point P are formed at
    points Q and R respectively.
(a) The light waves from the two slits are coherent.
...................................................................................................................................................
............................................................................................................................................. [1]
(i) the difference in their path lengths, in nm, from the slits
    (d) The intensity of the light incident on the double slit is increased without changing the
        frequency.
         Describe how the appearance of the fringes after this change is different from, and similar to,
         their appearance before the change.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [3]
(e) The light of wavelength 660 nm is now replaced by blue light from a laser.
         State and explain the change, if any, that must be made to the separation of the two slits so
         that the fringe separation on the screen is the same as it was for light of wavelength 660 nm.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
[Total: 11]
5 6. A horizontal string is stretched between two fixed points A and B. A vibrator is used to oscillate the
     string and produce an observable stationary wave.
point P
A B
Fig. 5.1
    The dots in the diagram represent the positions of the nodes on the string. Point P on the string is
    moving downwards.
The wave on the string has a speed of 35 m s–1 and a period of 0.040 s.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
    (b) On Fig. 5.1, sketch a line to show a possible position of the string a quarter of a cycle later
        than the position shown in the diagram.                                                     [1]
    (d) A particle on the string has zero displacement at time t = 0. From time t = 0 to time t = 0.060 s,
        the particle moves through a total distance of 72 mm.
[Total: 8]
5 7. (a) (i) State the conditions required for the formation of a stationary wave.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
         (ii)   State the phase difference between any two vibrating particles in a stationary wave
                between two adjacent nodes.
    (b) A motorcycle is travelling at 13.0 m s–1 along a straight road. The rider of the motorcycle sees
        a pedestrian standing in the road directly ahead and operates a horn to emit a warning sound.
        The pedestrian hears the warning sound from the horn at a frequency of 543 Hz. The speed
        of the sound in the air is 334 m s–1.
(i) Calculate the frequency, to three significant figures, of the sound emitted by the horn.
         (ii)   The motorcycle rider passes the stationary pedestrian and then moves directly away from
                her. As the rider moves away, he operates the horn for a second time. The pedestrian
                now hears sound that is increasing in frequency.
                State the variation, if any, in the speed of the motorcycle when the rider operates the
                horn for the second time.
..................................................................................................................................... [1]
    (c) A beam of vertically polarised monochromatic light is incident normally on a polarising filter,
        as shown in Fig. 5.1.
                                                                 polarising
                                                                 filter
intensity I0 intensity IT
                                                                 transmission
                                                                 axis of filter
Fig. 5.1
         The filter is positioned with its transmission axis at an angle of 20° to the vertical.
         The incident light has intensity I0 and the transmitted light has intensity IT.
                                           IT
          (i)   By considering the ratio      , calculate the ratio
                                           I0
         (ii)   The filter is now rotated, about the direction of the light beam, from its starting position
                shown in Fig. 5.1. The direction of rotation is such that the angle of the transmission axis
                to the vertical initially increases.
                Calculate the minimum angle through which the filter must be rotated so that the intensity
                of the transmitted light returns to the value that it had when the filter was at its starting
                position.
                                                                                                                    [Total: 10]
© UCLES 2022                                      9702/22/F/M/22                                                   [Turn over
     9702/22/O/N/21 Q5                                                    12
5 8. A tube is initially fully submerged in water. The axis of the tube is kept vertical as the tube is slowly
     raised out of the water, as shown in Fig. 5.1.
loudspeaker
                                                                                                  surface of water
                                    air column
                                                                                                       water
                           wall of
                           tube
Fig. 5.1
     A loudspeaker producing sound of frequency 530 Hz is positioned at the open top end of the tube
     as it is raised. The water surface inside the tube is always level with the water surface outside the
     tube. The speed of the sound in the air column in the tube is 340 m s–1.
     (a) Describe a simple way that a student, without requiring any additional equipment, can detect
         when a stationary wave is formed in the air column as the tube is being raised.
...................................................................................................................................................
............................................................................................................................................. [1]
     (b) Determine the height of the top end of the tube above the surface of the water when a
         stationary wave is first produced in the tube. Assume that an antinode is formed level with the
         top of the tube.
    (c) Determine the distance moved by the tube between the positions at which the first and
        second stationary waves are formed.
[Total: 5]
4 9. (a) By reference to the direction of transfer of energy, state what is meant by a longitudinal wave.
...................................................................................................................................................
............................................................................................................................................. [1]
    (b) A vehicle travels at constant speed around a wide circular track. It continuously sounds its
        horn, which emits a single note of frequency 1.2 kHz. An observer is a large distance away
        from the track, as shown in the view from above in Fig. 4.1.
direction of travel
vehicle
                                                                                                                           observer
                                                                             track
         Fig. 4.2 shows the variation with time of the frequency f of the sound of the horn that is
         detected by the observer. The time taken for the vehicle to travel once around the track is T.
1.6
f / kHz
1.4
1.2
1.0
                    0.8
                          0                                   T                                    2T                                   3T
                                                                                                                    time
Fig. 4.2
          (i)   Explain why the frequency of the sound detected by the observer is sometimes above
                and sometimes below 1.2 kHz.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
..................................................................................................................................... [1]
        (iii)   On Fig. 4.1, mark with a letter X the position of the vehicle when it emitted the sound that
                is detected at time T.                                                                   [1]
        (iv)    On Fig. 4.1, mark with a letter Y the position of the vehicle when it emitted the sound that
                                    9T
                is detected at time    .                                                                 [1]
                                     4
    (c) The speed of the sound in the air is 320 m s–1.
[Total: 9]
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
(b) Two waves, with intensities I and 4I, superpose. The waves have the same frequency.
    (c) Coherent light of wavelength 550 nm is incident normally on a double slit of slit separation
        0.35 mm. A series of bright and dark fringes forms on a screen placed a distance of 1.2 m
        from the double slit, as shown in Fig. 4.1. The screen is parallel to the double slit.
screen
                                                                          1.2 m
                 light
0.35 mm
           wavelength
            550 nm                  double
                                      slit
(i) Determine the distance between the centres of adjacent bright fringes on the screen.
(ii) The light of wavelength 550 nm is replaced with red light of a single frequency.
                State and explain the change, if any, in the distance between the centres of adjacent
                bright fringes.
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [1]
[Total: 8]
411. (a) For a progressive wave, state what is meant by its period.
...................................................................................................................................................
............................................................................................................................................. [1]
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
    (c) Electromagnetic waves of wavelength 0.040 m are emitted in phase from two sources X and
        Y and travel in a vacuum. The arrangement of the sources is shown in Fig. 4.1.
                                          X                                                      path of
                                                                                                 detector
                                                             1.380 m
Y 1.240 m
         A detector moves along a path that is parallel to the line XY. A pattern of intensity maxima and
         minima is detected.
          (i)    State the name of the region of the electromagnetic spectrum that contains the waves
                 from X and Y.
..................................................................................................................................... [1]
        (iii)   Show that the path difference at point Z between the waves from X and Y is 3.5 λ, where λ
                is the wavelength of the waves.
[1]
(v) The waves from X alone have the same amplitude at point Z as the waves from Y alone.
..................................................................................................................................... [1]
        (vi)    The frequencies of the waves from X and Y are both decreased to the same lower value.
                The waves stay within the same region of the electromagnetic spectrum.
                Describe the effect of this change on the pattern of intensity maxima and minima along
                the path of the detector.
...........................................................................................................................................
..................................................................................................................................... [1]
[Total: 11]
...................................................................................................................................................
............................................................................................................................................. [1]
(c) The light from the laser is incident normally on a diffraction grating.
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
    (d) A diffraction grating is used with different wavelengths of visible light. The angle θ of the
        fourth-order maximum from the zero-order (central) maximum is measured for each
        wavelength. The variation with wavelength λ of sin θ is shown in Fig. 4.1.
sin θ
                                            0
                                                0                                400                         700
                                                                                              λ / nm
Fig. 4.1
                Determine an expression, in terms of G, for the distance d between the centres of two
                adjacent slits in the diffraction grating.
d = ......................................................... [2]
         (ii)   On Fig. 4.1, sketch a graph to show the results that would be obtained for the
                second-order maxima.                                                        [2]
[Total: 10]
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
    (b) A transmitter produces microwaves that travel in air towards a metal plate, as shown in
        Fig. 4.1.
                 microwave                                                                                    metal
                 transmitter                                     microwave                                    plate
                                                                  receiver
Fig. 4.1
         The microwaves have a wavelength of 0.040 m. A stationary wave is formed between the
         transmitter and the plate.
...........................................................................................................................................
..................................................................................................................................... [1]
                1.   Determine the shortest distance from X of the receiver when it detects another
                     intensity minimum.
distance = ........................................................... m
                2.   Determine the number of intensity maxima that are detected by the receiver as it
                     moves from X to a position that is 9.1 cm away from X.
                                                     number = ...............................................................
                                                                                                                         [2]
[Total: 8]
                                    horizontal circular
                                    path of source,
                                    radius 2.4 m
                            rope       source
                                       of sound
                                                                                            distant
                                                                                           observer
    The source moves with a speed of 12.0 m s−1 and emits sound of frequency 951 Hz. The speed of
    the sound in the air is 330 m s−1. An observer, standing a very long distance away from the source,
    hears the sound.
    (a) Calculate the minimum frequency, to three significant figures, of the sound heard by the
        observer.
         Determine the shortest time interval between the observer hearing sound of minimum
         frequency and the observer hearing sound of maximum frequency.
[Total: 4]
515. Microwaves with the same wavelength and amplitude are emitted in phase from two sources X
     and Y, as shown in Fig. 5.1.
                                                                       path of detector
        X
    A microwave detector is moved along a path parallel to the line joining X and Y. An interference
    pattern is detected. A central intensity maximum is located at point A and there is an adjacent
    intensity minimum at point B. The microwaves have a wavelength of 0.040 m.
    (c) The amplitudes of the waves from the sources are changed. This causes a change in the
        amplitude of the waves arriving at point A. At this point, the amplitude of the wave arriving from
        source X is doubled and the amplitude of the wave arriving from source Y is also doubled.
Describe the effect, if any, on the intensity of the central maximum at point A.
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
    (d) Describe the effect, if any, on the positions of the central intensity maximum and the adjacent
        intensity minimum due to the following separate changes.
...........................................................................................................................................
..................................................................................................................................... [1]
         (ii)    The phase difference between the microwaves emitted by the sources X and Y changes
                 to 180°.
...........................................................................................................................................
..................................................................................................................................... [1]
[Total: 9]
516. A progressive wave Y passes a point P. The variation with time t of the displacement x for the
     wave at P is shown in Fig. 5.1.
6.0
                                        4.0
                              x / mm
                                        2.0
                                         0
                                              0    0.1    0.2       0.3     0.4 0.5
                                                                               t/s
                                       –2.0
–4.0
–6.0
Fig. 5.1
    (b) A second wave Z has wavelength 8.0 cm and amplitude 2.0 mm at point P. Waves Y and Z
        have the same speed.
                                              intensity of wave Z
                                                                  .
                                              intensity of wave Y
[Total: 5]
617. (a) Describe the conditions required for two waves to be able to form a stationary wave.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [2]
    (b) A stationary wave on a string has nodes and antinodes. The distance between a node and an
        adjacent antinode is 6.0 cm.
..................................................................................................................................... [1]
(ii) Calculate the wavelength of the two waves forming the stationary wave.
        (iii)    State the phase difference between the particles at two adjacent antinodes of the
                 stationary wave.
[Total: 5]
418. Two progressive sound waves Y and Z meet at a fixed point P. The variation with time t of the
     displacement x of each wave at point P is shown in Fig. 4.1.
                                    4                                                     wave Y
                              x / μm
                                       2
                                       0
                                           0               1.0                 2.0              3.0 t / ms 4.0
                                     –2
                                                                                                           wave Z
                                     –4
–6
Fig. 4.1
(a) Use Fig. 4.1 to state one quantity of waves Y and Z that is:
..................................................................................................................................... [1]
(ii) different.
..................................................................................................................................... [1]
...................................................................................................................................................
............................................................................................................................................. [1]
    (d) The two waves superpose at P. Use Fig. 4.1 to determine the resultant displacement at time
        t = 0.75 ms.
[Total: 10]
19.
4   (a) State the difference between progressive waves and stationary waves in terms of the transfer
         of energy along the wave.
...................................................................................................................................................
............................................................................................................................................. [1]
    (b) A progressive wave travels from left to right along a stretched string. Fig. 4.1 shows part of
        the string at one instant.
                                                                                               R                 direction of
                                                                                                                 wave travel
                                               Q
                                        P
                    string
                                                               0.48 m
Fig. 4.1
         P, Q and R are three different points on the string. The distance between P and R is 0.48 m.
         The wave has a period of 0.020 s.
        (iv)    Fig. 4.1 shows the position of the string at time t = 0. Describe how the displacement of
                point Q on the string varies with time from t = 0 to t = 0.010 s.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
    (c) A stationary wave is formed on a different string that is stretched between two fixed points
        X and Y. Fig. 4.2 shows the position of the string when each point is at its maximum
        displacement.
                                   X                                                                      Y
                                                                               Z
Fig. 4.2
..................................................................................................................................... [1]
(ii) State the number of antinodes of the wave shown in Fig. 4.2.
(iii) State the phase difference between points W and Z on the string.
        (iv)    A new stationary wave is now formed on the string. The new wave has a frequency
                that is half of the frequency of the wave shown in Fig. 4.2. The speed of the wave is
                unchanged.
                On Fig. 4.3, draw a position of the string, for this new wave, when each point is at its
                maximum displacement.
X Y
                                                                   Fig. 4.3
                                                                                                                                                       [1]
                                                                                                                                           [Total: 11]
© UCLES 2020                                                     9702/22/M/J/20                                                          [Turn over
                                                                         12
     9702/22/M/J/20 Q5
5
20. One end of a wire is attached to a fixed point. A force F is applied to the wire to cause extension x.
     The variation with F of x is shown in Fig. 5.1.
0.6
                              0.5
                        x / mm
                              0.4
0.3
0.2
0.1
                                     0
                                         0       5       10       15       20       25       30       35        40       45
                                                                                                   F/N
Fig. 5.1
     The wire has a cross-sectional area of 4.1 × 10–7 m2 and is made of metal of Young modulus
     1.7 × 1011 Pa. Assume that the cross-sectional area of the wire remains constant as the wire
     extends.
(a) State the name of the law that describes the relationship between F and x shown in Fig. 5.1.
............................................................................................................................................. [1]
Determine:
421. (a) (i)    By reference to the direction of propagation of energy, state what is meant by a
                longitudinal wave.
...........................................................................................................................................
..................................................................................................................................... [1]
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
(b) The wavelength of light from a laser is determined using the apparatus shown in Fig. 4.1.
                                   double
                                     slit                                                                                  screen
                light
3.7 × 10 –4 m
2.3 m
         The light from the laser is incident normally on the plane of the double slit.
         The separation of the two slits is 3.7 × 10–4 m. The screen is parallel to the plane of the double
         slit. The distance between the screen and the double slit is 2.3 m.
         A pattern of bright fringes and dark fringes is seen on the screen. The separation of adjacent
         bright fringes on the screen is 4.3 × 10–3 m.
         (ii)   The intensity of the light passing through each slit was initially the same. The intensity of
                the light through one of the slits is now reduced.
Compare the appearance of the fringes before and after the change of intensity.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
[Total: 8]
4
22. (a) For a progressive wave, state what is meant by:
...........................................................................................................................................
..................................................................................................................................... [1]
...........................................................................................................................................
..................................................................................................................................... [1]
          (i)   Diffraction of the light waves occurs at each slit of the grating. The light waves emerging
                from the slits are coherent.
1. diffraction
....................................................................................................................................
.............................................................................................................................. [1]
2. coherent.
....................................................................................................................................
.............................................................................................................................. [1]
         (ii)   The wavelength of the laser light is 650 nm. The angle between the third order diffraction
                maxima is 68°, as illustrated in Fig. 4.1.
                                                                                                       third order
                                                                                                       diffraction maximum
                    laser light
                                                                          68°
                wavelength 650 nm
                                                                                                       third order
                                                          diffraction                                  diffraction maximum
                                                           grating
Calculate the separation d between the centres of adjacent slits of the grating.
d = ..................................................... m [3]
(iii) The red laser light is replaced with blue laser light.
                State and explain the change, if any, to the angle between the third order diffraction
                maxima.
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
[Total: 9]
...................................................................................................................................................
............................................................................................................................................. [1]
    (b) A cathode-ray oscilloscope (CRO) is used to analyse a sound wave. The screen of the CRO
        is shown in Fig. 5.1.
1 cm
1 cm
Fig. 5.1
    (c) The source emitting the sound in (b) is at point A. Waves travel from the source to point C
        along two different paths, AC and ABC, as shown in Fig. 5.2.
                                                           20.8 m                          C
                                        A
                                           8.0 m
                                                                                                  reflecting
                                                             B                                     surface
         Distance AB is 8.0 m and distance AC is 20.8 m. Angle ABC is 90°. Assume that there is no
         phase change of the sound wave due to the reflection at point B. The wavelength of the
         waves is 1.6 m.
(i) Show that the waves meeting at C have a path difference of 6.4 m.
[1]
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [2]
        (iii)   Determine the difference between the times taken for the sound to travel from the source
                to point C along the two different paths.
        (iv)    The wavelength of the sound is gradually increased. Calculate the wavelength of the
                sound when an intensity maximum is next detected at point C.
                                                                                                                                             [Total: 9]
© UCLES 2019                                                      9702/22/O/N/19                                                         [Turn over
    9702/21/O/N/19 Q5                                                     12
D1 D2
Fig. 5.1
The lines in the diagram represent crests. The waves have a wavelength of 6.0 cm.
    (a) One condition that is required for an observable interference pattern is that the waves must
        be coherent.
          (i)    Describe how the apparatus is arranged to ensure that the waves from the dippers are
                 coherent.
...........................................................................................................................................
..................................................................................................................................... [1]
         (ii)    State one other condition that must be satisfied by the waves in order for the interference
                 pattern to be observable.
...........................................................................................................................................
..................................................................................................................................... [1]
    (b) Light from a lamp above the ripple tank shines through the water onto a screen below the
        tank. Describe one way of seeing the illuminated pattern more clearly.
...................................................................................................................................................
............................................................................................................................................. [1]
(c) The speed of the waves is 0.40 m s–1. Calculate the period of the waves.
    (d) Fig. 5.1 shows a point X that lies on a crest of the wave from D1 and midway between two
        adjacent crests of the wave from D2.
    (e) On Fig. 5.1, draw one line, at least 4 cm long, which joins points where only maxima of the
        interference pattern are observed.                                                       [1]
[Total: 8]
525. A vertical tube of length 0.60 m is open at both ends, as shown in Fig. 5.1.
tube
N 0.60 m
                                                                             direction of
                                                                             incident
                                                                             sound wave
Fig. 5.1
    An incident sinusoidal sound wave of a single frequency travels up the tube. A stationary wave
    is then formed in the air column in the tube with antinodes A at both ends and a node N at the
    midpoint.
(a) Explain how the stationary wave is formed from the incident sound wave.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[2]
    (b) On Fig. 5.2, sketch a graph to show the variation of the amplitude of the stationary wave with
        height h above the bottom of the tube.
amplitude
                                                   0
                                                       0              0.20               0.40              0.60
                                                                                                h/m
                                                                     Fig. 5.2
                                                                                                                                                         [2]
          (i)   the direction of the oscillations of an air particle at a height of 0.15 m above the bottom of
                the tube
.......................................................................................................................................[1]
         (ii)   the phase difference between the oscillations of a particle at a height of 0.10 m and a
                particle at a height of 0.20 m above the bottom of the tube.
Determine the frequency of the wave when a stationary wave is next formed.
[Total: 9]
426. (a) For a progressive water wave, state what is meant by:
(i) displacement
...........................................................................................................................................
.......................................................................................................................................[1]
(ii) amplitude.
...........................................................................................................................................
.......................................................................................................................................[1]
    (b) Two coherent waves X and Y meet at a point and superpose. The phase difference between
        the waves at the point is 180°. Wave X has an amplitude of 1.2 cm and intensity I. Wave Y
        has an amplitude of 3.6 cm.
    (c) (i)     Monochromatic light is incident on a diffraction grating. Describe the diffraction of the
                light waves as they pass through the grating.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
         (ii)   A parallel beam of light consists of two wavelengths 540 nm and 630 nm. The light is
                incident normally on a diffraction grating. Third-order diffraction maxima are produced for
                each of the two wavelengths. No higher orders are produced for either wavelength.
d = ...................................................... m [3]
        (iii)   The beam of light in (c)(ii) is replaced by a beam of blue light incident on the same
                diffraction grating.
                State and explain whether a third-order diffraction maximum is produced for this blue
                light.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
[Total: 11]
(i) State expressions, in terms of some or all of the symbols f, λ and N, for:
distance = ...............................................................
2. time t.
                                                          time t = ...............................................................
                                                                                                                              [2]
         (ii)   Use your answers in (i) to deduce the equation relating the speed v of the sound wave to
                f and λ.
[1]
    (b) The waveform of a sound wave is displayed on the screen of a cathode-ray oscilloscope
        (c.r.o.), as shown in Fig. 5.1.
1.0 cm
1.0 cm
Fig. 5.1
(c) Two sources S1 and S2 of sound waves are positioned as shown in Fig. 5.2.
                                      S1
                                                                                                         X
                                                                                                    L
                                                                                                    Q
                                      S2
                                                                                                    L
                                                           7.40 m                                   Q
                                                                                                    L
                                                                                                           Y
         The sources emit coherent sound waves of wavelength 0.85 m. A sound detector is moved
         parallel to the line S1S2 from a point X to a point Y. Alternate positions of maximum loudness
         L and minimum loudness Q are detected, as illustrated in Fig. 5.2.
...........................................................................................................................................
.......................................................................................................................................[1]
         (ii)   State the phase difference between the two waves arriving at the position of minimum
                loudness Q that is closest to point X.
[Total: 9]
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
...........................................................................................................................................
.......................................................................................................................................[1]
    (b) Two coherent waves P and Q meet at a point in phase and superpose. Wave P has an
        amplitude of 1.5 cm and intensity I. The resultant intensity at the point where the waves meet
        is 3I.
(c) The apparatus shown in Fig. 5.1 is used to produce an interference pattern on a screen.
                    laser light
                wavelength 680 nm                                              a
                                                                                                  D
                                                                double-slit                                                screen
Distance D is varied from 2.0 m to 3.5 m. The variation with D of x is shown in Fig. 5.2.
10.0
                                      8.0
                             x / mm
                                      6.0
4.0
2.0
                                       0
                                        2.0        2.5              3.0              3.5
                                                          D/m
Fig. 5.2
a = ...................................................... m [3]
(ii) The laser is now replaced by another laser that emits light of a shorter wavelength.
                On Fig. 5.2, sketch a possible line to show the variation with D of x for the fringes that
                are now produced.                                                                       [2]
[Total: 10]
429. (a) Sound waves are longitudinal waves. By reference to the direction of propagation of energy,
         state what is meant by a longitudinal wave.
...................................................................................................................................................
...............................................................................................................................................[1]
    (b) A stationary sound wave in air has amplitude A. In an experiment, a detector is used to
        determine A2. The variation of A2 with distance x along the wave is shown in Fig. 4.1.
4.0
                          3.0
     A2 / arbitrary
             units
                          2.0
1.0
                             0
                                 0                10                20                 30                40                 50                60
                                                                                                                                   x / cm
Fig. 4.1
          (i)    State the phase difference between the vibrations of an air particle at x = 25 cm and the
                 vibrations of an air particle at x = 50 cm.
         (ii)    The speed of the sound in the air is 330 m s–1. Determine the frequency of the sound
                 wave.
ratio = ...........................................................[2]
                                                                                                                                               [Total: 7]
© UCLES 2018                                                      9702/22/O/N/18
    9702/22/O/N/18 Q5                             11
5
30. Red light of wavelength 640 nm is incident normally on a diffraction grating having a line spacing
    of 1.7 × 10–6 m, as shown in Fig. 5.1.
second order
    The second order diffraction maximum of the light is at an angle θ to the direction of the incident
    light.
[3]
    (b) Determine a different wavelength of visible light that will also produce a diffraction maximum
        at an angle of 49°.
[Total: 5]
4
31. (a) State the principle of superposition.
...................................................................................................................................................
...................................................................................................................................................
.............................................................................................................................................. [2]
(b) An arrangement for demonstrating the interference of light is shown in Fig. 4.1.
                                                                                                                                        B
                                                                                                                                 P      D
                                                                                                                                 Q      B
                                                                                                                                        D
   light                                                                                                                                          central
wavelength                            a                                                                            22 mm                B          bright
 610 nm                                                                                                                                            fringe
                                                                                                                                        D
                                                                                                                                        B
                                                                                                                                        D
                                                                                                                                        B
                                                                               2.7 m
                                                                                                                                 screen
                         double
                           slit
         The wavelength of the light is 610 nm. The distance between the double slit and the screen
         is 2.7 m.
         An interference pattern of bright fringes and dark fringes is observed on the screen. The
         centres of the bright fringes are labelled B and centres of the dark fringes are labelled D.
         Point P is the centre of a particular dark fringe and point Q is the centre of a particular bright
         fringe, as shown in Fig. 4.1. The distance across five bright fringes is 22 mm.
(i) The light waves leaving the two slits are coherent.
...........................................................................................................................................
...................................................................................................................................... [1]
a = ...................................................... m [3]
        (iv)    A higher frequency of visible light is now used. State and explain the change to the
                separation of the fringes.
...........................................................................................................................................
...................................................................................................................................... [1]
         (v)    The intensity of the light incident on the double slit is now increased without altering
                its frequency. Compare the appearance of the fringes after this change with their
                appearance before this change.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
[Total: 11]
532. (a) State the relationship between the intensity and the amplitude of a wave.
...................................................................................................................................................
...............................................................................................................................................[1]
    (b) Microwaves of the same amplitude and wavelength are emitted in phase from two sources P
        and Q. The sources are arranged as shown in Fig. 5.1.
                             P
                                                      1.840 m
2.020 m
                                                                                                  path of detector
                            Q
Fig. 5.1
         A microwave detector is moved along a path that is parallel to the line joining P and Q. A series
         of intensity maxima and intensity minima are detected.
         When the detector is at a point X, the distance PX is 1.840 m and the distance QX is 2.020 m.
         The microwaves have a wavelength of 6.0 cm.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[3]
        (iii)   Describe the effect on the interference pattern along the path of the detector due to each
                of the following separate changes.
....................................................................................................................................
....................................................................................................................................
                2.   The phase difference between the microwaves emitted from the sources changes to
                     180°.
....................................................................................................................................
                     ....................................................................................................................................
                                                                                                                                                     [2]
[Total: 8]
...........................................................................................................................................
.......................................................................................................................................[1]
...........................................................................................................................................
.......................................................................................................................................[1]
    (b) A loudspeaker producing sound of constant frequency is placed near the open end of a pipe,
        as shown in Fig. 4.1.
                                                                 pipe                          piston
                                                                                                                          loudspeaker
Fig. 4.1
         A movable piston is at distance x from the open end of the pipe. Distance x is increased from
         x = 0 by moving the piston to the left with a constant speed of 0.75 cm s–1.
          (i)   A much louder sound is first heard when x = 4.5 cm. Assume that there is an antinode of
                a stationary wave at the open end of the pipe.
         (ii)   After a time interval, a second much louder sound is heard. Calculate the time interval
                between the first louder sound and the second louder sound being heard.
[Total: 7]
...........................................................................................................................................
.......................................................................................................................................[1]
...........................................................................................................................................
.......................................................................................................................................[1]
    (b) Fig. 4.1 shows the variation with time t of the displacement x of two progressive waves P and
        Q passing the same point.
4.0
                                 3.0
                       x / mm
                                 2.0                                                                            wave P
1.0
                                    0
                                        0              0.20               0.40              0.60               0.80 t / s
                               –1.0                                                                             wave Q
–2.0
–3.0
–4.0
Fig. 4.1
                                         intensity of wave Q
                                                             .
                                         intensity of wave P
        (iv)    The two waves superpose as they pass the same point. Use Fig. 4.1 to determine the
                resultant displacement at time t = 0.45 s.
[Total: 8]
535. (a) When monochromatic light is incident normally on a diffraction grating, the emergent light
         waves have been diffracted and are coherent.
...........................................................................................................................................
.......................................................................................................................................[1]
...........................................................................................................................................
.......................................................................................................................................[1]
(b) Light consisting of only two wavelengths λ1 and λ2 is incident normally on a diffraction grating.
         The third order diffraction maximum of the light of wavelength λ1 and the fourth order
         diffraction maximum of the light of wavelength λ2 are at the same angle θ to the direction of
         the incident light.
          (i)
                                   λ
                Show that the ratio 2 is 0.75.
                                              λ1
                Explain your working.
[2]
λ1 = .................................................... nm [1]
[Total: 5]
436. (a) State the conditions required for the formation of a stationary wave.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[2]
    (b) The sound from a loudspeaker is detected by a microphone that is connected to a cathode-ray
        oscilloscope (c.r.o.). Fig. 4.1 shows the trace on the screen of the c.r.o.
1 cm
1 cm
Fig. 4.1
In air, the sound wave has a speed of 330 m s–1 and a wavelength of 0.18 m.
        (iii)    The intensity of the sound from the loudspeaker is now halved. The wavelength of
                 the sound is unchanged. Assume that the amplitude of the trace is proportional to the
                 amplitude of the sound wave.
On Fig. 4.1, sketch the new trace shown on the screen of the c.r.o. [2]
(c) The loudspeaker in (b) is held above a vertical tube of liquid, as shown in Fig. 4.2.
loudspeaker
                      liquid
                                                level A                                            level A
tube
                                                level B                                            level B
                                                                  liquid
tap
         A tap at the bottom of the tube is opened so that liquid drains out at a constant rate. The
         wavelength of the sound from the loudspeaker is 0.18 m. The sound that is heard first
         becomes much louder when the liquid surface reaches level A. The next time that the sound
         becomes much louder is when the liquid surface reaches level B, as shown in Fig. 4.3.
         (ii)    On Fig. 4.3, label with the letter N the positions of the nodes of the stationary wave that
                 is formed in the air column when the liquid surface is at level B.                      [1]
        (iii)    The mass of liquid leaving the tube per unit time is 6.7 g s–1. The tube has an internal
                 cross-sectional area of 13 cm2. The density of the liquid is 0.79 g cm–3.
Calculate the time taken for the liquid to move from level A to level B.
                                                                                                                 [Total: 12]
© UCLES 2018                                     9702/22/F/M/18                                                 [Turn over
     9702/22/O/N/17 Q4                                                    10
437. (a) State the conditions required for the formation of a stationary wave.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[2]
    (b) A horizontal string is stretched between two fixed points X and Y. The string is made to vibrate
        vertically so that a stationary wave is formed. At one instant, each particle of the string is at its
        maximum displacement, as shown in Fig. 4.1.
                                       string
                                                                  Q
                X                                                                                                                      Y
                                                     P
                                                                       2.0 m
Fig. 4.1
         P and Q are two particles of the string. The string vibrates with a frequency of 40 Hz. Distance
         XY is 2.0 m.
number = ...........................................................[1]
         (ii)       Determine the minimum time taken for the particle P to travel from its lowest point to its
                    highest point.
        (iii)       State the phase difference, with its unit, between the vibrations of particle P and of
                    particle Q.
[Total: 8]
...........................................................................................................................................
.......................................................................................................................................[1]
...........................................................................................................................................
.......................................................................................................................................[1]
    (b) A tube is open at both ends. A loudspeaker, emitting sound of a single frequency, is placed
        near one end of the tube, as shown in Fig. 3.1.
tube
A A A A
      loudspeaker
                                                                                  0.60 m
Fig. 3.1
         The speed of the sound in the tube is 340 m s–1. The length of the tube is 0.60 m.
         A stationary wave is formed with an antinode A at each end of the tube and two antinodes
         inside the tube.
...........................................................................................................................................
.......................................................................................................................................[1]
1. the wavelength,
2. the frequency.
        (iv)   Determine the minimum frequency of the sound from the loudspeaker that produces a
               stationary wave in the tube.
[Total: 9]
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
                      ....................................................................................................................................
                                                                                                                                                      [3]
    (b) A diffraction grating is used with different wavelengths of light. The angle θ of the second
        order maximum is measured for each wavelength. The variation with wavelength λ of sin θ is
        shown in Fig. 5.1.
0.60
sin θ
0.50
0.40
0.30
0.20
                         0.10
                            300                  350               400                450               500                550
                                                                                                                λ / nm
                                                                   Fig. 5.1
© UCLES 2017                                                     9702/23/M/J/17
                                                     13
gradient = ...........................................................[2]
         (ii)   Use the gradient determined in (i) to calculate the slit separation d of the diffraction
                grating.
d = .......................................................m [2]
        (iii)   On Fig. 5.1, sketch a line to show the results that would be obtained for the first order
                maxima.                                                                                [1]
[Total: 10]
...................................................................................................................................................
...............................................................................................................................................[1]
    (b) An object A of mass 100 g is moving in a straight line with a velocity of 0.60 m s–1 to the right.
        An object B of mass 200 g is moving in the same straight line as object A with a velocity of
        0.80 m s–1 to the left, as shown in Fig. 4.1.
                                      A                                                                        B
                                                   0.60 m s–1                        0.80 m s–1
                                   100 g                                                                    200 g
Fig. 4.1
Objects A and B collide. Object A then moves with a velocity of 0.40 m s–1 to the left.
Explain how the collision is inelastic and still obeys the law of conservation of energy.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[1]
                                                                                                                                               [Total: 4]
     9702/22/M/J/17 Q5
...................................................................................................................................................
...............................................................................................................................................[1]
    (b) A sound wave travels through air. Describe the motion of the air particles relative to the
        direction of travel of the sound wave.
...................................................................................................................................................
          ...............................................................................................................................................[1]
© UCLES 2017                                                       9702/22/M/J/17
                                                                      11
    (c) The sound wave emitted from the horn of a stationary car is detected with a microphone and
        displayed on a cathode-ray oscilloscope (c.r.o.), as shown in Fig. 5.1.
1.0 cm
                                                                                                      1.0 cm
                                                                 Fig. 5.1
(i) Use Fig. 5.1 to determine the frequency of the sound wave.
         (ii)   The horn of the car sounds continuously. Describe the changes to the trace seen on the
                c.r.o. as the car travels at constant speed
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
                     ....................................................................................................................................
                                                                                                                                                     [3]
[Total: 7]
641. (a) Interference fringes may be observed using a light-emitting laser to illuminate a double slit.
         The double slit acts as two sources of light.
Explain
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
(ii) the reason why a double slit is used rather than two separate sources of light.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[1]
    (b) A laser emitting light of a single wavelength is used to illuminate slits S1 and S2, as shown in
        Fig. 6.1.
                                   S1
                     laser
                                          0.48 mm
                     light         S2
                                                                                               screen
2.4 m
         An interference pattern is observed on the screen AB. The separation of the slits is 0.48 mm.
         The slits are 2.4 m from AB. The distance on the screen across 16 fringes is 36 mm, as
         illustrated in Fig. 6.2.
16 fringes
36 mm
Fig. 6.2
    (c) Two dippers D1 and D2 are used to produce identical waves on the surface of water, as
        illustrated in Fig. 6.3.
                                                                                              P
                                                                     7.2 cm
D1
11.2 cm water
D2
         The wavelength of the waves is 1.6 cm. The phase difference between the waves produced
         at D1 and D2 is zero.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
         (ii)   State and explain the effect on the answer to (c)(i) if the apparatus is changed so that,
                separately,
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
2. the intensity of the wave from D1 is less than the intensity of that from D2.
....................................................................................................................................
....................................................................................................................................
                      ....................................................................................................................................
                                                                                                                                                      [2]
[Total: 10]
442. (a) State the conditions required for the formation of stationary waves.
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[2]
    (b) One end of a string is attached to a vibrator. The string is stretched by passing the other end
        over a pulley and attaching a load, as illustrated in Fig. 4.1.
                                                              string
                                                                                                                                  pulley
                                                                   A                                                      B
     vibrator
                                                                                                                                   support for
                                                                                                                                     pulley
                                                                                                                                     load
Fig. 4.1
         The frequency of vibration of the vibrator is adjusted to 250 Hz and a transverse wave travels
         along the string with a speed of 12 m s–1. The wave is reflected at the pulley and a stationary
         wave forms on the string.
Fig. 4.2 shows the string between points A and B at time t = t1.
string
A B
Fig. 4.2
(ii) On Fig. 4.2, sketch the position of the string between A and B at times
[3]
[Total: 7]
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[1]
    (b) A car travels with a constant velocity along a straight road. The car horn with a frequency of
        400 Hz is sounded continuously. A stationary observer on the roadside hears the sound from
        the horn at a frequency of 360 Hz.
        The speed of sound is 340 m s–1.
Determine the magnitude v, and the direction, of the velocity of the car relative to the observer.
v = .......................................................m s–1
                                                                               direction ...............................................................
                                                                                                                                                    [3]
[Total: 4]
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[2]
    (b) A child sits on a rotating horizontal platform in a playground. The child moves with a constant
        speed along a circular path, as illustrated in Fig. 4.1.
                                                                         Q
                                        circular
                                          path
                                                                                                                                 to a distant
                                                                                                                                  observer
                                                                         P        7.5 m s–1
                                                         child
Fig. 4.1
         An observer is standing a long distance away from the child. During one particular revolution,
         the child, moving at a speed of 7.5 m s–1, starts blowing a whistle at point P and stops blowing
         it at point Q on the circular path.
The whistle emits sound of frequency 950 Hz. The speed of sound in air is 330 m s–1.
(i) Determine the maximum frequency of the sound heard by the distant observer.
(ii) Describe the variation in the frequency of the sound heard by the distant observer.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
[Total: 6]
...................................................................................................................................................
...............................................................................................................................................[2]
(b) An arrangement for demonstrating the interference of light is shown in Fig. 4.1.
                                                                                '
                                             double slit                                                screen
         The wavelength of the light from the laser is 580 nm. The separation of the slits is 0.41 mm.
         The perpendicular distance between the double slit and the screen is D.
         Coherent light emerges from the slits and an interference pattern is observed on the screen.
         The central bright fringe is produced at point X. The closest dark fringes to point X are
         produced at points Y and Z. The distance XY is 2.0 mm.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
(ii) State the difference in the distances, in nm, from each slit to point Y.
D = ...................................................... m [3]
        (iv)    The intensity of the light passing through the two slits was initially the same. The intensity
                of the light through one of the slits is now reduced. Compare the appearance of the
                fringes before and after the change of intensity.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
[Total: 10]
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[2]
    (b) A cathode-ray oscilloscope (c.r.o.) is used to determine the frequency of the sound emitted by
        a loudspeaker. The trace produced on the screen of the c.r.o. is shown in Fig. 4.1.
                                                                                                      1 cm
                                                                                         1 cm
Fig. 4.1
[2]
    (c) The loudspeaker in (b) emits the sound in all directions. A person attaches the loudspeaker to
        a string and then swings the loudspeaker at a constant speed in a horizontal circle above his
        head.
         An observer, standing a large distance away from the loudspeaker, hears sound of maximum
         frequency 1640 Hz. The speed of sound in air is 330 m s–1.
         (ii)    Describe and explain, qualitatively, the variation in the frequency of the sound heard by
                 the observer.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
                                                                                                                                               [Total: 8]
     9702/21/O/N/16 Q5
...................................................................................................................................................
...............................................................................................................................................[2]
    (b) Laser light of wavelength 500 nm is incident normally on a diffraction grating. The resulting
        diffraction pattern has diffraction maxima up to and including the fourth-order maximum.
Calculate, for the diffraction grating, the minimum possible line spacing.
    (c) The light in (b) is now replaced with red light. State and explain whether this is likely to result
        in the formation of a fifth-order diffraction maximum.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...............................................................................................................................................[2]
[Total: 7]
      frequency
      generator                                             light string
                                                                                                                                   pulley
                                          vibrator                                                                                 wheel
masses
Fig. 7.1
          (i)   Describe two adjustments that can be made to the apparatus to produce stationary
                waves on the string.
1. .......................................................................................................................................
...........................................................................................................................................
2. .......................................................................................................................................
                ...........................................................................................................................................
                                                                                                                                                       [2]
         (ii)   Describe the features that are seen on the stretched string that indicate stationary waves
                have been produced.
...................................................................................................................................... [1]
    (b) The variation with time t of the displacement x of a particle caused by a progressive wave R is
        shown in Fig. 7.2. For the same particle, the variation with time t of the displacement x caused
        by a second wave S is also shown in Fig. 7.2.
                          4.0
                                               R
                          3.0
                x / cm    2.0
                                                     S
                          1.0
                           0
                                0     0.2             0.4              0.6              0.8               1.0
                                                                                                  t /s
                         ï
ï
ï
ï
Fig. 7.2
          (i)   Determine the phase difference between wave R and wave S. Include an appropriate
                unit.
[Total: 6]
49. (a) By reference to the direction of the propagation of energy, state what is meant by a longitudinal
4
        wave and by a transverse wave.
longitudinal: ...............................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
transverse: ................................................................................................................................
...................................................................................................................................................
          ...................................................................................................................................................
                                                                                                                                                         [2]
Ι = Kvρ f 2A2
Show that both sides of the equation have the same SΙ base units.
[3]
...........................................................................................................................................
.......................................................................................................................................[1]
State the effect of the motion on the light observed from the star.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[1]
    (d) A car travels at a constant speed towards a stationary observer. The horn of the car sounds at
        a frequency of 510 Hz and the observer hears a frequency of 550 Hz. The speed of sound in
        air is 340 m s–1.
[Total: 10]
550. (a) Light of a single wavelength is incident on a diffraction grating. Explain the part played by
         diffraction and interference in the production of the first order maximum by the diffraction
         grating.
diffraction: .................................................................................................................................
...................................................................................................................................................
interference: ..............................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
          ...................................................................................................................................................
                                                                                                                                                         [3]
(b) The diffraction grating illustrated in Fig. 5.1 is used with light of wavelength 486 nm.
second order
                                                                                                   first order
                              light
                        wavelength 486 nm
                                                                         59.4°                    zero order
                                                        diffraction
                                                         grating                                   first order
         The orders of the maxima produced are shown on the screen in Fig. 5.1. The angle between
         the two second order maxima is 59.4°.
                                                                                                                                               [Total: 6]
© UCLES 2016                                                       9702/22/M/J/16                                                          [Turn over
    9702/21/M/J/16 Q5                              11
551. The variation with time t of the displacement y of a wave X, as it passes a point P, is shown in
     Fig. 5.1.
4.0
                        3.0
               \ / cm
                                                                                          ZDYH;
                        2.0
1.0
                         0
                              0     1.0         2.0            3.0            4.0             5.0
                                                                                     W / ms
                    –1.0
–2.0
–3.0
–4.0
Fig. 5.1
    (b) A second wave Z with the same frequency as wave X also passes point P.
        Wave Z has intensity 2I. The phase difference between the two waves is 90°.
On Fig. 5.1, sketch the variation with time t of the displacement y of wave Z.
[3]
    (c) A double-slit interference experiment is used to determine the wavelength of light emitted
        from a laser, as shown in Fig. 5.2.
0.45 mm
laser light
         The separation of the slits is 0.45 mm. The fringes are viewed on a screen at a distance D
         from the double slit.
         The fringe width x is measured for different distances D. The variation with D of x is shown in
         Fig. 5.3.
5.0
                                 4.0
                        [ / mm
                                 3.0
2.0
1.0
                                  0
                                   1.5       2.0           2.5              3.0           3.5
                                                                                  '/m
Fig. 5.3
          (i)   Use the gradient of the line in Fig. 5.3 to determine the wavelength, in nm, of the laser
                light.
         (ii)   The separation of the slits is increased. State and explain the effects, if any, on the graph
                of Fig. 5.3.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
[Total: 11]
452. (a) (i)    By reference to the direction of propagation of energy, state what is meant by a transverse
                wave.
...........................................................................................................................................
...................................................................................................................................... [1]
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
    (b) Circular water waves may be produced by vibrating dippers at points P and Q, as illustrated in
        Fig. 4.1.
                                                                         wavefront
                                                   P
                                                                           44 cm
                                                                                             R
                                                                                  29 cm
                                                                 Q
         The waves from P alone have the same amplitude at point R as the waves from Q alone.
         Distance PR is 44 cm and distance QR is 29 cm.
The dippers vibrate in phase with a period of 1.5 s to produce waves of speed 4.0 cm s−1.
         (ii)   By reference to the distances PR and QR, explain why the water particles are at rest at
                point R.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [3]
    (c) A wave is produced on the surface of a different liquid. At one particular time, the variation of
        the vertical displacement y with distance x along the surface of the liquid is shown in Fig. 4.2.
                     1.0
           y / cm
                     0.5
                       0
                           0                 2                 4                  6                 8                 10        x / cm
                    –0.5
–1.0
Fig. 4.2
(i) The wave has intensity I1 at distance x = 2.0 cm and intensity I2 at x = 10.0 cm.
                                                                intensity I2
                                                                             .
                                                                intensity I1
         (ii)   State the phase difference, with its unit, between the oscillations of the liquid particles at
                distances x = 3.0 cm and x = 4.0 cm.
[Total: 11]