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8 A student uses a tank of water to observe waves on the surface of the water.
(a) The graph in Fig. 8.1 represents a wave on the surface of the water.
displacement
of water
0
distance
Fig. 8.1
(i) Draw on Fig. 8.1 to indicate the amplitude of the wave. Label the amplitude A. [1]
(ii) Draw on Fig. 8.1 to indicate one wavelength of the wave. Label the wavelength L. [1]
(b) The student creates waves in the water tank and places various barriers in their path.
(i) Fig. 8.2 shows the wavefronts as they approach a barrier placed at an angle of 45° to the
wavefronts.
wavefronts
water barrier
tank direction of
travel of
wavefronts
45°
water
Fig. 8.2
On Fig. 8.2, draw three wavefronts after they have reflected from the barrier. Draw an
arrow to show the direction of travel of these wavefronts. [2]
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(ii) The student replaces the barrier in Fig. 8.2 with a different barrier, as shown in Fig. 8.3.
Fig. 8.3 shows the wavefronts as they reach the barrier.
wavefronts barrier
water
tank
direction of
travel of
wavefronts
water narrow
gap
Fig. 8.3
On Fig. 8.3, draw three wavefronts after they have passed through the narrow gap. [2]
[Total: 6]
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6 Fig. 6.1 is a full-scale diagram that represents a sound wave travelling in air.
direction of travel
Fig. 6.1
(a) On Fig. 6.1, mark two points, each at the centre of a different compression. Label both of the
points C. [1]
(b) The speed of sound in air is 330 m / s.
Measure the diagram and determine the frequency of the sound.
frequency = ......................................................... [3]
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(c) The wave reaches a barrier. Fig. 6.2 shows the wave passing through a gap in the barrier.
barrier
direction of travel
Fig. 6.2
The frequency of the wave is increased to a value many times greater than the value obtained
in (b).
Describe and explain two ways in which a diagram representing the wave with the greater
frequency differs from Fig. 6.2.
1. ..............................................................................................................................................
...................................................................................................................................................
2. ..............................................................................................................................................
...................................................................................................................................................
[3]
[Total: 7]
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6 Fig. 6.1 shows a shallow tank viewed from above. The depth of the water is different in the two
parts of the tank. Fig. 6.1 shows the crests and the troughs of a wave that pass from left to right.
boundary
45°
Key
trough
crest
33°
2.6 cm
Fig. 6.1 (not to scale)
As the wave passes from one side to the other, the direction of the wavefronts changes.
(a) Explain why the direction of the wavefronts changes in the way shown in Fig. 6.1.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [3]
(b) The speed of the wave in the left-hand part of the tank is 0.39 m / s.
(i) Using information from Fig. 6.1, determine the frequency of the wave.
frequency = ......................................................... [3]
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(ii) Determine the speed of the wave in the right-hand side of the tank.
speed = ......................................................... [3]
[Total: 9]
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5 Fig. 5.1 shows crests of a wave approaching a barrier where the wave is reflected.
direction of travel of wave
crest
barrier
Fig. 5.1
(a) On Fig. 5.1, draw three crests of the reflected wave. [3]
(b) The wave has a wavelength of 36 cm and a speed of 1.2 m / s.
Calculate the frequency of the wave.
frequency = ......................................................... [3]
(c) Complete the following sentences.
An echo is the name for a reflected .................................................................. wave.
The waves that form an echo are a type of longitudinal wave. Longitudinal waves are made
up of .................................................................. and rarefactions.
[2]
[Total: 8]
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