Daul Nature & Matter Wave

Practice Problems www.neetphysicskota.com

1. Kinetic energy with which the electrons are emitted from the metal surface due to photoelectric
effect is
(a) Independent of the intensity of illumination
(b) Independent of the frequency of light
(c) Inversely proportional to the intensity of illumination
(d) Directly proportional to the intensity of illumination

2. The threshold wavelength for photoelectric emission from a material is 5200 Å. Photo-electrons
will be emitted when this material is illuminated with monochromatic radiation from a
(a) 50 watt infrared lamp
(b) 1 watt infrared lamp
(c) 50 watt ultraviolet lamp
(d) 1 watt ultraviolet lamp
(e) Both (c) and (d)

3. Threshold frequency for a metal is 1015 Hz. Light of  = 4000 Å falls on its surface. Which of the
following statements is correct
(a) No photoelectric emission takes place
(b) Photo-electrons come out with zero speed
(c) Photo-electrons come out with 103 m/sec speed
(d) Photo-electrons come out with 105 m/sec speed

4. Photo cells are used for the

(a) Reproduction of pictures from the cinema film
(b) Reproduction of sound from the cinema film
(c) Automatic switching of street light
(d) (b) and (c) both

5. The work function of a metal is 4.2 eV, its threshold wavelength will be
(a) 4000 Å (b) 3500 Å (c) 2955 Å (d) 2500 Å

6. The number of photo-electrons emitted per second from a metal surface increases when
(a) The energy of incident photons increases
(b) The frequency of incident light increases

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 (c) The wavelength of the incident light increases
(d) The intensity of the incident light increases

7. The work function of metal is 1 eV. Light of wavelength 3000 Å is incident on this metal surface.
The velocity of emitted photo-electrons will be
(a) 10 m/sec (b) 1 10 3 m/sec (c) 1 10 4 m/sec (d) 1 10 6 m/sec

8. The retarding potential for having zero photo-electron current

(a) Is proportional to the wavelength of incident light
(b) Increases uniformly with the increase in the wavelength of incident light
(c) Is proportional to the frequency of incident light
(d) Increases uniformly with the increase in the frequency of incident light wave

9. In a dark room of photography, generally red light is used. The reason is

(a) Most of the photographic films are not sensitive to red light
(b) The frequency for red light is low and hence the energy hv of photons is less
(c) (a) and (b) both
(d) None of the above

10. The work function of a metal is 1.6  10 −19 J. When the metal surface is illuminated by the light of
wavelength 6400 Å, then the maximum kinetic energy of emitted photo-electrons will be
(Planck's constant h = 6.4  10 −34 Js )
(a) 14  10 −19 J (b) 2.8  10 −19 J (c) 1.4  10 −19 J (d) 1.4  10−19 eV

11. Ultraviolet radiations of 6.2 eV falls on an aluminium surface (work function 4.2 eV ). The kinetic
energy in joules of the fastest electron emitted is approximately
(a) 3.2  10 −21 (b) 3.2  10 −19 (c) 3.2  10 −17 (d) 3.2  10 −15

12. The work function for tungsten and sodium are 4.5 eV and 2.3 eV respectively. If the threshold
wavelength  for sodium is 5460 Å , the value of  for tungsten is
(a) 5893 Å (b) 10683 Å (c) 2791 Å (d) 528 Å

13. A photon of energy 3.4 eV is incident on a metal having work function 2 eV. The maximum K.E.
of photo-electrons is equal to
(a) 1.4 eV (b) 1.7 eV (c) 5.4 eV (d) 6.8 eV

14. The work function of a metallic surface is 5.01 eV. The photo-electrons are emitted when light of
wavelength 2000Å falls on it. The potential difference applied to stop the fastest photo-electrons
is [h = 4.14  10 −15 eV sec]
(a) 1.2 volts (b) 2.24 volts (c) 3.6 volts (d) 4.8 volts
15. The photoelectric threshold wavelength for a metal surface is 6600 Å. The work function for this
is
(a) 1.87 V (b) 1.87 eV (c) 18.7 eV (d) 0.18 eV

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16. In a photoelectric experiment for 4000 Å incident radiation, the potential difference to stop the
ejection is 2 V. If the incident light is changed to 3000 Å, then the potential required to stop the
ejection of electrons will be
(a) 2 V (b) Less than 2 V (c) Zero (d) Greater than 2 V

17. Light of wavelength 4000 Å is incident on a sodium surface for which the threshold wave length
of photo – electrons is 5420 Å. The work function of sodium is
(a) 4.58 eV (b) 2.29 eV (c) 1.14 eV (d) 0.57 eV

18. Photo cell is a device to

(a) Store photons
(b) Measure light intensity
(c) Convert photon energy into mechanical energy
(d) Store electrical energy for replacing storage batteries

19. If the work function for a certain metal is 3.2  10−19 joule and it is illuminated with light of
frequency 8  1014 Hz. The maximum kinetic energy of the photo-electrons would be
(a) 2.1  10−19 J (b) 8.5  10−19 J (c) 5.3  10−19 J (d) 3.2  10−19 J
(h = 6.63  10 −34 Js)

20. Stopping potential for photoelectrons

(a) Does not depend on the frequency of the incident light
(b) Does not depend upon the nature of the cathode material
(c) Depends on both the frequency of the incident light and nature of the cathode material
(d) Depends upon the intensity of the incident light

21. The maximum wavelength of radiation that can produce photoelectric effect in a certain metal is
200 nm. The maximum kinetic energy acquired by electron due to radiation of wavelength 100
nm will be
(a) 12.4 eV (b) 6.2 eV (c) 100 eV (d) 200 eV

22. When the light source is kept 20 cm away from a photo cell, stopping potential 0.6 V is obtained.
When source is kept 40 cm away, the stopping potential will be
(a) 0.3 V (b) 0.6 V (c) 1.2 V (d) 2.4 V

23. The minimum energy required to remove an electron is called

(a) Stopping potential (b) Kinetic energy
(c) Work function (d) None of these

24. Light of wavelength 4000 Å falls on a photosensitive metal and a negative 2V potential stops the
emitted electrons. The work function of the material (in eV) is approximately
(h = 6.6  10 −34 Js, e = 1.6  10 −19 C, c = 3  10 8 ms −1 )

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 (a) 1.1 (b) 2.0 (c) 2.2 (d) 3.1

25. Assuming photoemission to take place, the factor by which the maximum velocity of the emitted
photoelectrons changes when the wavelength of the incident radiation is increased four times, is

1 1
(a) 4 (b) (c) 2 (d)
4 2

26. Work function of a metal is 2.51 eV. Its threshold frequency is

(a) 5.9  1014 cycle/sec (b) 6.5  1014 cycle/sec
(c) 9.4  1014 cycle/sec (d) 6.08  1014 cycle/sec

27. Energy conversion in a photoelectric cell takes place from

(a) Chemical to electrical (b) Magnetic to electrical
(c) Optical to electrical (d) Mechanical to electrical

28. Which one of the following is true in photoelectric emission

(a) Photoelectric current is directly proportional to the amplitude of light of a given frequency
(b) Photoelectric current is directly proportional to the intensity of light of a given frequency at
moderate intensities
(c) Above the threshold frequency, the maximum K.E. of photoelectrons is inversely proportional
to the frequency of incident light
(d) The threshold frequency depends upon the wavelength of incident light

29. When a point source of light is at a distance of one metre from a photo cell, the cut off voltage is
found to be V. If the same source is placed at 2 m distance from photo cell, the cut off voltage
will be
(a) V (b) V/2 (c) V/4 (d) V / 2

30. The work function of a photoelectric material is 3.3 eV. The threshold frequency will be equal to
(a) 8  104 Hz (b) 8  1056 Hz (c) 8  1010 Hz (d) 8  1014 Hz

31. If the work function of a metal is '  ' and the frequency of the incident light is ' ' , there is no
emission of photoelectron if
   
(a)   (b)  = (c)   (d)   = 
h h h h

32. A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted
to 2 m then
(a) Number of electrons emitted is half the initial number
(b) Each emitted electron carries half the initial energy
(c) Number of electrons emitted is a quarter of the initial number
(d) Each emitted electron carries one quarter of the initial energy

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33. Light of wavelength  strikes a photo-sensitive surface and electrons are ejected with kinetic
energy E. If the kinetic energy is to be increased to 2E, the wavelength must be changed to  '
where
 
(a)  ' = (b)  ' = 2 (c)  '   (d)  '  
2 2

34. If in a photoelectric experiment, the wavelength of incident radiation is reduced from 6000 Å to
4000 Å then
(a) Stopping potential will decrease
(b) Stopping potential will increase
(c) Kinetic energy of emitted electrons will decrease
(d) The value of work function will decrease

35. The photoelectric work function for a metal surface is 4.125 eV. The cut-off wavelength for this
surface is
(a) 4125 Å (b) 2062.5 Å (c) 3000 Å (d) 6000 Å

36. As the intensity of incident light increases

(a) Photoelectric current increases
(b) Photoelectric current decreases
(c) Kinetic energy of emitted photoelectrons increases
(d) Kinetic energy of emitted photoelectrons decreases

37. Light of wavelength 5000 Å falls on a sensitive plate with photoelectric work function of 1.9 eV.
The kinetic energy of the photoelectron emitted will be
(a) 0.58 eV (b) 2.48 eV (c) 1.24 eV (d) 1.16 eV

38. Which of the following is dependent on the intensity of incident radiation in a photoelectric
experiment
(a) Work function of the surface
(b) Amount of photoelectric current
(c) Stopping potential will be reduced
(d) Maximum kinetic energy of photoelectrons

39. The work function of a substance is 4.0 eV. The longest wavelength of light that can cause
photoelectron emission from this substance is approximately
(a) 540 nm (b) 400 nm (c) 310 nm (d) 220 nm

40. The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy
6 eV fall on it is 4 eV. The stopping potential in volts is
(a) 2 (b) 4 (c) 6 (d) 10

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41. Work function of a metal is 2.1 eV. Which of the waves of the following wavelengths will be able
to emit photoelectrons from its surface
(a) 4000 Å, 7500 Å (b) 5500 Å, 6000 Å (c) 4000 Å, 6000 Å (d) None of these

42. If mean wavelength of light radiated by 100 W lamp is 5000 Å, then number of photons radiated
per second are
(a) 3 10 23 (b) 2.5  10 22 (c) 2.5  10 20 (d) 5  1017

43. The frequency of the incident light falling on a photosensitive metal plate is doubled, the kinetic
energy of the emitted photoelectrons is
(a) Double the earlier value (b) Unchanged
(c) More than doubled (d) Less than doubled

44. When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons
are liberated. For another emitter, however light of 600 nm wavelength is sufficient for creating
photoemission. What is the ratio of the work functions of the two emitters
(a) 1 : 2 (b) 2 : 1 (c) 4 : 1 (d) 1 : 4

45. Threshold wavelength for photoelectric effect on sodium is 5000 Å. Its work function is
(a) 15 J (b) 16  10−14 J (c) 4  10−19 J (d) 4  10−81 J

46. The cathode of a photoelectric cell is changed such that the work function changes from W1 to
W2 (W2>W1). If the current before and after change are I1 and I2, all other conditions remaining
unchanged, then (assuming h > W2)
(a) I1 = I 2 (b) I1  I 2 (c) I1  I 2 (d) I1  I 2  2I1

47. A beam of light of wavelength  and with illumination L falls on a clean surface of sodium. If N
photoelectrons are emitted each with kinetic energy E, then
1
(a) N  L and E  L (b) N  L and E 

1 1
(c) N   and E  L (d) N  and E 
 L
48. Which of the following statements is correct
(a) The current in a photocell increases with increasing frequency of light
(b) The photocurrent is proportional to applied voltage
(c) The photocurrent increases with increasing intensity of light
(d) The stopping potential increases with increasing intensity of incident light

49. What is the stopping potential when the metal with work function 0.6 eV is illuminated with the
light of 2 eV
(a) 2.6 V (b) 3.6 V (c) 0.8 V (d) 1.4 V

50. When yellow light is incident on a surface, no electrons are emitted while green light can emit. If
red light is incident on the surface, then
(a) No electrons are emitted

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 (b) Photons are emitted
(c) Electrons of higher energy are emitted
(d) Electrons of lower energy are emitted

51. The photoelectric threshold wavelength of a certain metal is 3000Å. If the radiation of 2000Å is
incident on the metal
(a) Electrons will be emitted
(b) Positrons will be emitted
(c) Protons will be emitted
(d) Electrons will not be emitted

52. A photocell stops emission if it is maintained at 2V negative potential. The energy of most
energetic photoelectron is
(a) 2eV (b) 2J (c) 2kJ (d) 2keV

53. The work functions for sodium and copper are 2eV and 4 eV . Which of them is suitable for a
photocell with 4000 Å light
(a) Copper (b) Sodium (c) Both (d) Neither of them

54. For intensity I of a light of wavelength 5000Å the photoelectron saturation current is 0.40  A
and stopping potential is 1.36 V, the work function of metal is
(a) 2.47 eV (b) 1.36 eV (c) 1.10 eV (d) 0.43 eV

55. The work function of aluminium is 4.2 eV . If two photons, each of energy 3.5 eV strike an electron
of aluminium, then emission of electrons will be
(a) Possible
(b) Not possible
(c) Data is incomplete
(d) Depend upon the density of the surface

56. In photoelectric effect if the intensity of light is doubled then maximum kinetic energy of
photoelectrons will become
(a) Double (b) Half (c) Four time (d) No change

57. Energy required to remove an electron from aluminium surface is 4.2 eV. If light of wavelength
2000 Å falls on the surface, the velocity of the fastest electron ejected from the surface will be (a)
8.4  105 m/sec (b) 7.4  105 m/sec (c) 6.4  105 m/sec (d) 8.4  106 m/sec

58. Mercury violet light ( = 4558 Å) is falling on a photosensitive material ( = 2.5eV ) . The speed of
the ejected electrons is in ms−1 , about
(a) 3  105 (b) 2.65  105 (c) 4  104 (d) 3.65  107

59. The work functions of metals A and B are in the ratio 1 : 2. If light of frequencies f and 2 f are
incident on the surfaces of A and B respectively, the ratio of the maximum kinetic energies of

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 photoelectrons emitted is (f is greater than threshold frequency of A, 2f is greater than threshold
frequency of B)
(a) 1 : 1 (b) 1 : 2 (c) 1 : 3 (d) 1 : 4

60. Light of frequency  is incident on a substance of threshold frequency 0(0 < ). The energy of
the emitted photo-electron will be
(a) h( −  0 ) (b) h /  (c) he ( −  0 ) (d) h /  0

61. The stopping potential (V0 )

(a) Depends upon the angle of incident light
(b) Depends upon the intensity of incident light
(c) Depends upon the surface nature of the substance
(d) Is independent of the intensity of the incident light

62. If work function of metal is 3 eV then threshold wavelength will be

(a) 4125 Å (b) 4000 Å (c) 4500 Å (d) 5000 Å

63. When wavelength of incident photon is decreased then

(a) Velocity of emitted photo-electron decreases
(b) Velocity of emitted photoelectron increases
(c) Velocity of photoelectron do not charge
(d) Photo electric current increases

64. Quantam nature of light is explained by which of the following phenomenon

(a) Huygen wave theory
(b) Photoelectric effect
(c) Maxwell electromagnetic theory
(d) de-Broglie theory

65. When a metal surface is illuminated by light of wavelengths 400 nm and 250 nm, the maximum
velocities of the photoelectrons ejected are v and 2v respectively. The work function of the metal
is (h = Planck’s constant, c = velocity of light in air)
(a) 2 hc  106 J (b) 1.5 hc  10 6 J (c) hc  106 J (d) 0.5 hc  10 6 J

66. 4 eV is the energy of the incident photon and the work function in 2eV . What is the stopping
potential
(a) 2V (b) 4V (c) 6V (d) 2 2V

67. Light of frequency  is incident on a certain photoelectric substance with threshold frequency 0.
The work function for the substance is
(a) h (b) h0 (c) h( −  0 ) (d) h( +  0 )

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68. If threshold wavelength for sodium is 6800Å then the work function will be [RPET 2001]
(a) 1.8eV (b) 2.5eV (c) 2.1eV (d) 1.4eV

69. If intensity of incident light is increased in PEE then which of the following is true
(a) Maximum K.E. of ejected electron will increase
(b) Work function will remain unchanged
(c) Stopping potential will decrease
(d) Maximum K.E. of ejected electron will decrease

70. Light of frequency 8  1015 Hz is incident on a substance of photoelectric work function 6.125 eV .
The maximum kinetic energy of the emitted photoelectrons is
(a) 17 eV (b) 22 eV (c) 27 eV (d) 37 eV

71. The photoelectric threshold wavelength for potassium (work function being 2eV ) is
(a) 310 nm (b) 620 nm (c) 1200 nm (d) 2100 nm

72. Photons of energy 6 eV are incident on a metal surface whose work function is 4 eV. The
minimum kinetic energy of the emitted photo-electrons will be
(a) 0 eV (b) 1 eV (c) 2 eV (d) 10 eV

73. According to photon theory of light which of the following physical quantities associated with a
photon do not/does not change as it collides with an electron in vacuum
(a) Energy and momentum (b) Speed and momentum
(c) Speed only (d) Energy only

74. The lowest frequency of light that will cause the emission of photoelectrons from the surface of a
metal (for which work function is 1.65 eV) will be
(a) 4  1010 Hz (b) 4  1011 Hz (c) 4  1014 Hz (d) 4  10−10 Hz

75. Light of two different frequencies whose photons have energies 1eV and 2.5eV respectively,
successively illuminates a metal of work function 0.5eV . The ratio of maximum kinetic energy of
the emitted electron will be
(a) 1 : 5 (b) 1 : 4 (c) 1 : 2 (d) 1 : 1

76. Sodium and copper have work functions 2.3 eV and 4.5 eV respectively. Then the ratio of their
threshold wavelengths is nearest to
(a) 1: 2 (b) 4 : 1 (c) 2 : 1 (d) 1 : 4

77. Photon of 5.5 eV energy fall on the surface of the metal emitting photoelectrons of maximum
kinetic energy 4.0 eV. The stopping voltage required for these electrons are
(a) 5.5 V (b) 1.5 V (c) 9.5 V (d) 4.0 V

78. A caesium photocell, with a steady potential difference of 60V across, is illuminated by a bright
point source of light 50 cm away. When the same light is placed 1m away the photoelectrons
emitted from the cell
(a) Are one quarter as numerous

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 (b) Are half as numerous
(c) Each carry one quarter of their previous momentum
(d) Each carry one quarter of their previous energy

79. A radio transmitter radiates 1 kW power at a wavelength 198.6 metres. How many photons does
it emit per second
(a) 1010 (b) 10 20 (c) 1030 (d) 1040

80. Two identical photo-cathodes receive light of frequencies f1 and f2 . If the velocities of the photo
electrons (of mass m ) coming out are respectively v1 and v2 , then
1/ 2
2h 2h
(a) v1 − v2 =  ( f1 − f2 ) (b) v12 − v22 = ( f1 − f2 )
m  m
1/ 2
2h 2h
(c) v1 + v2 =  ( f1 + f2 ) (d) v12 + v22 = ( f1 + f2 )
m  m

81. Consider the two following statements A and B and identify the correct choice given in the
answers;
(A) In photovlotaic cells the photoelectric current produced is not proportional to the, intensity
of incident light.
(B) In gas filled photoemissive cells, the velocity of photoelectrons depends on the wavelength of
the incident radiation.
(a) Both A and B are true (b) Both A and B are false
(c) A is true but B is false (d) A is false B is true

82. When radiation of wavelength  is incident on a metallic surface, the stopping potential is 4.8
volts. If the same surface is illuminated with radiation of double the wavelength, then the stopping
potential becomes 1.6 volts. Then the threshold wavelength for the surface is
(a) 2 (b) 4  (c) 6 (d) 8 

83. The frequency and work function of an incident photon are  and 0 . If 0 is the threshold
frequency then necessary condition for the emission of photo electron is
0
(a)    0 (b)  = (c)    0 (d) None of these
2

84. Light of wavelength 1824 Å, incident on the surface of a metal, produces photo-electrons with
maximum energy 5.3 eV. When light of wavelength 1216 Å is used, the maximum energy of
photoelectrons is 8.7 eV. The work function of the metal surface is
(a) 3.5 eV (b) 13.6 eV (c) 6.8 eV (d) 1.5 eV

85. If the energy of a photon corresponding to a wavelength of 6000 Å is 3.32  10−19 J , the photon
energy for a wavelength of 4000 Å will be
(a) 1.4 eV (b) 4.9 eV (c) 3.1 eV (d) 1.6 eV

86. If the wavelength of light is 4000 Å, then the number of waves in 1 mm length will be
(a) 25 (b) 0.25 (c) 0.25  104 (d) 25  104

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87. The velocity of photon is proportional to (where  is frequency)
2 1
(a) (b) (c)  (d) 
2 

88. If the work function of a photometal is 6.825 eV. Its threshold wavelength will be (c = 3  108 m / s)
(a) 1200 Å (b) 1800 Å (c) 2400 Å (d) 3600 Å

89. A photon of energy 8 eV is incident on a metal surface of threshold frequency 1.6  1015 Hz , then
the maximum kinetic energy of photoelectrons emitted is (h = 6.6  10−34 Js)
(a) 4.8 eV (b) 2.4 eV (c) 1.4 eV (d) 0.8 eV

90. If the de-Broglie wavelengths for a proton and for a  − particle are equal, then the ratio of their
velocities will be
(a) 4 : 1 (b) 2 : 1 (c) 1 : 2 (d) 1 : 4

91. The de-Broglie wavelength  associated with an electron having kinetic energy E is given by the
expression
h 2h 2 2mE
(a) (b) (c) 2mhE (d)
2mE mE h

92. Dual nature of radiation is shown by

(a) Diffraction and reflection
(b) Refraction and diffraction
(c) Photoelectric effect alone
(d) Photoelectric effect and diffraction

93. For the Bohr's first orbit of circumference 2r , the de-Broglie wavelength of revolving electron
will be
1 1
(a) 2r (b) r (c) (d)
2r 4r

94. An electron of mass m when accelerated through a potential difference V has de-Broglie
wavelength  . The de-Broglie wavelength associated with a proton of mass M accelerated
through the same potential difference will be
m m M M
(a)  (b)  (c)  (d) 
M M m m

95. What will be the ratio of de-Broglie wavelengths of proton and  − particle of same energy
(a) 2 : 1 (b) 1 : 2 (c) 4 : 1 (d) 1 : 4

96. What is the de-Broglie wavelength of the  − particle accelerated through a potential difference V
0.287 12.27 0.101 0.202
(a) Å (b) Å (c) Å (d) Å
V V V V

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97. de-Broglie hypothesis treated electrons as
(a) Particles (b) Waves (c) Both ‘a’ and ‘b’ (d) None of these

98. The energy that should be added to an electron, to reduce its de-Broglie wavelengths from 10−10
m to 0.5  10−10 m, will be
(a) Four times the initial energy
(b) Thrice the initial energy
(c) Equal to the initial energy
(d) Twice the initial energy

99. The de-Broglie wavelength of an electron having 80eV of energy is nearly

(1eV = 1.6  10–19 J, Mass of electron = 9  10–31kg Plank’s constant = 6.6  10–34 J-sec)
(a) 140 Å (b) 0.14 Å (c) 14 Å (d) 1.4 Å

100. If particles are moving with same velocity, then maximum de-Broglie wavelength will be for
(a) Neutron (b) Proton (c) -particle (d)  -particle

101. If an electron and a photon propagate in the form of waves having the same wavelength, it
implies that they have the same
(a) Energy (b) Momentum (c) Velocity (d) Angular momentum

102. The de-Broglie wavelength is proportional to

1 1 1
(a)   (b)   (c)   (d)   p
 m p

103. Particle nature and wave nature of electromagnetic waves and electrons can be shown by
(a) Electron has small mass, deflected by the metal sheet
(b) X-ray is diffracted, reflected by thick metal sheet
(c) Light is refracted and defracted
(d) Photoelectricity and electron microscopy

104. The de-Broglie wavelength of a particle moving with a velocity 2.25  108 m/s is equal to the
wavelength of photon. The ratio of kinetic energy of the particle to the energy of the photon is
(velocity of light is 3  108 m/s)
(a) 1/8 (b) 3/8 (c) 5/8 (d) 7/8

105. According to de-Broglie, the de-Broglie wavelength for electron in an orbit of hydrogen atom is
10–9 m. The principle quantum number for this electron is
(a) 1 (b) 2 (c) 3 (d) 4

106. The speed of an electron having a wavelength of 10−10 m is

(a) 7.25  10 6 m/s (b) 6.26  106 m / s (c) 5.25  106 m / s (d) 4.24  10 6 m / s

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107. The kinetic energy of electron and proton is 10 −32 J . Then the relation between their de-Broglie
wavelengths is
(a) p  e (b) p  e (c) p = e (d)  p = 2e

108. The de-Broglie wavelength of a particle accelerated with 150 volt potential is 10 −10 m. If it is
accelerated by 600 volts p.d., its wavelength will be
(a) 0.25 Å (b) 0.5 Å (c) 1.5 Å (d) 2 Å

109. The de-Broglie wavelength associated with a hydrogen molecule moving with a thermal velocity
of 3 km/s will be
(a) 1 Å (b) 0.66 Å (c) 6.6 Å (d) 66 Å

110. When the momentum of a proton is changed by an amount P0, the corresponding change in the
de-Broglie wavelength is found to be 0.25%. Then, the original momentum of the proton was
(a) p0 (b) 100 p0 (c) 400 p0 (d) 4 p0

111. The de-Broglie wavelength of a neutron at 27oC is . What will be its wavelength at 927oC
(a)  / 2 (b)  / 3 (c)  / 4 (d)  / 9

112. An electron and proton have the same de-Broglie wavelength. Then the kinetic energy of the
electron is
(a) Zero
(b) Infinity
(c) Equal to the kinetic energy of the proton
(d) Greater than the kinetic energy of the proton

113. For moving ball of cricket, the correct statement about de-Broglie wavelength is
(a) It is not applicable for such big particle
h
(b)
2mE
h
(c)
2mE
h
(d)
2mE

114. Photon and electron are given same energy (10−20 J ) . Wavelength associated with photon and
electron are  Ph and  el then correct statement will be
el
(a)  Ph  el (b)  Ph  el (c)  Ph = el (d) =C
Ph
115. The kinetic energy of an electron with de-Broglie wavelength of 0.3 nanometer is
(a) 0.168 eV (b) 16.8 eV (c) 1.68 eV (d) 2.5 eV

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116. A proton and an -particle are accelerated through a potential difference of 100 V. The ratio of
the wavelength associated with the proton to that associated with an -particle is
1
(a) 2 :1 (b) 2 : 1 (c) 2 2 : 1 (d) :1
2 2
117. The wavelength of de-Broglie wave is 2m, then its momentum is (h = 6.63  10–34 J-s)
(a) 3.315  10–28 kg-m/s (b) 1.66  10–28 kg-m/s
(c) 4.97  10–28 kg-m/s (d) 9.9  10–28 kg-m/s

118. de-Broglie wavelength of a body of mass 1 kg moving with velocity of 2000 m/s is
(a) 3.32  10–27 Å (b) 1.5  107 Å (c) 0.55  10–22 Å (d) None of these

119. The kinetic energy of an electron is 5 eV. Calculate the de-Broglie wavelength associated with it
(h = 6.6  10–34 Js, me = 9.1  10–31 kg)
(a) 5.47 Å (b) 10.9 Å (c) 2.7 Å (d) None of these

120. The wavelength associated with an electron accelerated through a potential difference of 100 V
is nearly
(a) 100 Å (b) 123 Å (c) 1.23 Å (d) 0.123 Å

121. The de-Broglie wavelength 

(a) is proportional to mass
(b) is proportional to impulse
(c) Inversely proportional to impulse
(d) does not depend on impulse

122. Davission and Germer experiment proved

(a) Wave nature of light (b) Particle nature of light
(c) Both (a) and (b) (d) Neither (a) nor (b)

123. If the kinetic energy of a free electron doubles, its de-Broglie wavelength changes by the factor
1 1
(a) (b) 2 (c) (d) 2
2 2

124. The energy that should be added to an electron to reduce its de Broglie wavelength from one
nm to 0.5 nm is
(a) Four times the initial energy (b)Equal to the initial energy
(c) Twice the initial energy (d)Thrice the initial energy

125. de-Broglie wavelength of a body of mass m and kinetic energy E is given by

h 2mE h h
(a)  = (b)  = (c)  = (d)  =
mE h 2mE 2mE

126. The wavelength of the matter wave is independent of

(a) Mass (b) Velocity (c) Momentum (d) Charge

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127. Which of the following figure represents the variation of particle momentum and the associated
de-Broglie wavelength
p p
(a) (b)

 
p
p
(c) (d)

 

128. The figure shows the variation of photocurrent with anode potential for a photo-sensitive surface
for three different radiations. Let I a , I b and I c be the intensities and fa , fb and fc be the frequencies
for the curves a, b and c respectively
Photo current
(a) fa = fb and la  lb
c b
(b) fa = fc and la = lc
a
(c) fa = fb and la = lb
O Anode potential
(d) fa = fb and la = lb

129. According to Einstein's photoelectric equation, the graph between the kinetic energy of
photoelectrons ejected and the frequency of incident radiation is
Kinetic energy

Kinetic energy

(a) (b)

Frequency Frequency
Kinetic energy

Kinetic energy

(c) (d)

Frequency Frequency

130. For the photoelectric effect, the maximum kinetic energy E k of the emitted photoelectrons is
plotted against the frequency  of the incident photons as shown in the figure. The slope of the
curve gives

Ek

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 (a) Charge of the electron
(b) Work function of the metal
(c) Planck's constant
(d) Ratio of the Planck’s constant to electronic charge

131. The stopping potential V for photoelectric emission from a metal surface is plotted along Y-axis
and frequency  of incident light along X-axis. A straight line is obtained as shown. Planck's
constant is given by
V Y

0 X


(a) Slope of the line

(b) Product of slope on the line and charge on the electron
(c) Product of intercept along Y-axis and mass of the electron
(d) Product of Slope and mass of electron

132. In an experiment on photoelectric effect the frequency f of the incident light is plotted against the
stopping potential V0 . The work function of the photoelectric surface is given by (e is electronic
charge)
Y
V0
(a) OB  e in eV A
X
O
0 
(b) OB in volt
(c) OA in eV B

(d) The slope of the line AB

133. The stopping potential as a function of the frequency of the incident radiation is plotted for two
different photoelectric surfaces A and B. The graphs show that work function of A is

A B
V

(a) Greater than that of B

(b)Smaller than that of B
(c) Equal to that of B
(d) No inference can be drawn about their work functions from the given graphs

134. The graph between intensity of light falling on a metallic plate (I) with the current (i) generated is

i i
(a) (b)

I I

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 i i
(c) (d)

I I

135. For a photoelectric cell the graph showing the variation of cut of voltage (Vo) with frequency ()
of incident light is best represented by
Vo Vo
(a) (b)

 
Vo
V0
(c) (d)

136. The curve between current (i) and potential difference (V) for a photo cell will be
i i
(a) (b)

V V

(c) i (d) i

V V

137. The correct curve between the stopping potential (V) and intensity of incident light (I) is
Vo
Vo
(a) (b)

I
I
Vo Vo
(c) (d)

I I

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138. The value of stopping potential in the following diagram
i (photoelectric

(a) – 4V current)
(b) – 3 V
(c) – 2V
(d) – 1 V
–4V –3V –2V –1V 0 V

139. In the following diagram if V2 > V1 then

i (Photoelectric
(a) 1 = 2
current)
(b) 1  2
(c) 1 = 2 2

(d) 1  2 1

V2 V1 Potential difference V

140. A point source of light is used in an experiment on photoelectric effect. Which of the following
curves best represents the variation of photo current (i) with distance (d) of the source from the
emitter
(a) a i a

(b) b b
c
d
(c) c
(d) d d

141. According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo
electrons from a metal versus the frequency, of the incident radiation gives a straight line whose
slope
(a) Is the same for all metals and independent of the intensity of the radiation
(b) Depends on the intensity of the radiation
(c) Depends both on the intensity of the radiation and the metal used
(d) Depends on the nature of the metals used

142. The stopping potential (V0 ) versus frequency () plot of a substance is shown in figure the
threshold wave length is
V0
2

4 5 6 7 8
 ×1014 Hz

(a) 5  1014 m
(b) 6000Å
(c) 5000 Å
(d) Can not be estimated from given data

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143. Figure represents a graph of kinetic energy (K) of photoelectrons (in eV) and frequency (v) for a
metal used as cathode in photoelectric experiment. The work function of metal is

(a) 1 eV K
3
(b) 1.5 eV 2
1
(c) 2 eV 0 
–1
(d) 3 eV
–2
–3

144. Figure represents the graph of photo current I versus applied voltage (V). The maximum energy
of the emitted photoelectrons is
i

(a) 2eV
(b) 4 eV
(c) 0 eV –4 –3 –2 –1 0 1 2 3 4
(d) 4J V

145. The graph that correctly represents the relation of frequency  of a particular characteristic X-ray
with the atomic number Z of the material is
 
(a) (b)

Z Z
I I
 

(c) (d)

Z Z
I I

146. The log-log graph between the energy E of an electron and its de-Broglie wavelength  will be

(a) (b)
log 

log 

log E log E

(c) (d)
log 

log 

log E log E

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147. The graph between the square root of the frequency of a specific line of characteristic spectrum
of X-rays and the atomic number of the target will be

(a) (b)

(c) (d)

Z Z

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 Answer Key

1. a 2. e 3. a 4. d 5. c 6. d 7. d
8. d 9. c 10. c 11. b 12. c 13. a 14. a
15. b 16 d 17 b 18 b 19 a 20 c 21 b
22 b 23 c 24 a 25 d 26 d 27 c 28 b
29 a 30 d 31 a 32 c 33 c 34 b 35 c
36 a 37 a 38 b 39 c 40 b 41 d 42 c
43 c 44 b 45 c 46 a 47 b 48 c 49 d
50 a 51 a 52 a 53 b 54 c 55 b 56 d
57 a 58 b 59 b 60 a 61 d 62 a 63 b
64 b 65 a 66 a 67 b 68 a 69 b 70 c
71 b 72 a 73 c 74 c 75 b 76 c 77 d
78 a 79 c 80 b 81 d 82 b 83 c 84 d
85 c 86 c 87 d 88 b 89 c 90 a 91 a
92 d 93 a 94 b 95 a 96 c 97 b 98 b
99 d 100 c 101 b 102 c 103 d 104 b 105 c
106 a 107 a 108 b 109 b 110 c 111 a 112 d
113 b 114 a 115 b 116 c 117 a 118 a 119 a
120 c 121 c 122 d 123 a 124 d 125 d 126 d
127 d 128 a 129 d 130 c 131 b 132 a 133 b
134 b 135 d 136 d 137 b 138 a 139 d 140 d
141 a 142 b 143 c 144 b 145 c 146 c 147 b

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