O-LevelPhysicsWaves5054/22 · May/June 2015 · Q913 Marks

Fig. 9.1 shows the wavefronts of a water wave in deep water in a ripple tank. [Figure 9.1] The frequency of the wave in deep water is 5.0Hz.

(a)Explain what is meant by the frequency of a wave.[2]
(b)(i)Determine the wavelength of the wave in deep water.[1]
(b)(ii)Calculate the speed of the wave in deep water. speed =[2]
(c)(i)The wave passes from deep water into shallow water. The speed of the wave is less in shallower water. State and explain how this affects the wavelength of the wave.[2]
(c)(ii)The wave in deep water shown in Fig. 9.2 travels towards the right and enters the shallow water at an angle. The wave refracts. [Figure 9.2] On Fig. 9.2, draw the wavefronts in the shallow water.[3]
(d)(i)Sound is also a wave. Describe one difference between a sound wave and a water wave.[2]
(d)(ii)The speed of sound in carbon dioxide gas is less than the speed of sound in air. Using this information, or otherwise, describe an experiment to show the refraction of sound waves. You may include a diagram of your apparatus.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2015). The mark or mark type is shown in brackets.

[1] (a) number of waves (that pass a point)
or number of oscillations (passing a point)
[1] (a) in unit time or per second or in 1 second
[1] (b) (i) 1.5 cm
[1] (b) (ii) (v = )fλ or 5 × 1.5 seen
or (s=)d/t and f = 1/t
[1] (b) (ii) 7.5cm/s
[1] (c) (i) wavelength decreases
[1] (c) (i) travels a shorter distance in the same time
or frequency stays the same (and v = fλ)
[1] (c) (ii) wavefronts with smaller wavelength (by eye)
[1] (c) (ii) smaller angle to surface (by eye) and slanted down
[1] (c) (ii) wavefronts join those in shallow water
[1] (d) (i) sound particles/wave/source • move backwards and forwards, water particles/wave/source • vibrate/oscillate/move at 90° to direction of (travel of) wave / move up and down
[1] (d) (i) sound (contains) compressions and rarefactions / or particles come closer/further apart, water (contains) crests and troughs
[1] (d) (i) sound speed 300-330m/s, water wave slower (than sound)
[1] (d) (ii) method of generating sound, e.g. (loud) speaker (and signal generator)
[1] (d) (ii) apparatus that enables refraction clear, e.g. carbon dioxide in balloon or any
shape where refraction is possible
[1] (d) (ii) method of detecting refraction, e.g. microphone and how it is used to show
refraction

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