O-LevelPhysicsWaves5054/22 · Oct/Nov 2022 · Q48 Marks

A sound wave, travelling in air or water, contains compressions and rarefactions.

(a)Describe an experiment to show that a medium is required to transmit sound waves. You may draw a labelled diagram if you wish.[3]
(b)When a sound wave passes through air or water, the molecules of the air or water move. Describe the motion of the molecules due to the sound wave.[2]
(c)Describe what is meant by 'a rarefaction'.[1]
(d)Fig. 4.1 shows a dolphin. [Figure 4.1] The range of audible sound frequencies for the dolphin is 75 Hz to 140 000 Hz. In water, the speed of sound is 1500 m/s. Calculate the smallest wavelength of sound in water that the dolphin can hear.[2]

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 (Oct/Nov 2022). The mark or mark type is shown in brackets.

[B1] equipment e.g. (evacuable) container and (suspended electric) bell / source of sound and (air) pump
[B1] action e.g. ringing / sound (produced) / sound heard and evacuate air/vacuum (produced)
[B1] observation e.g. transmission / hearing of sound ceases / no sound
[M1] (they) vibrate
[A1] (vibration) parallel to / in the direction of propagation / of energy travel
[B1] (point where) molecules are further apart (than average) or (point where) pressure / density is lower (than average)
[C1] (λ = ) v/ f or 1500/140 000
[A1] 1.1 x 10⁻² m or 1.1 cm or 11 mm

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