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GCSE Questions: Waves

Bats use the reflection of high pitched sound waves to determine the position of objects. The diagram below shows a bat and an insect flying in front of the bat.

(a) What determines the pitch of a sound wave? [1 mark]

Tick () one box as your answer.
Tick ()
amplitude
  
frequency
speed
  

 

(b) State the name given to reflected sound waves. [1 mark]

Echo

c) The bat emits sound waves with a range of wavelengths. Some of the sound waves will be diffracted by the insect.

Complete the following sentences to explain why. [2 marks]

Diffraction is caused by the sound waves spreading out ( 'changing direction' or 'moving apart' or 'bending' was insufficient to get you the mark) as they pass the insect. The most diffraction happens when the wavelength of the sound wave is the same size as the size of the insect.

(d) The bat emits a sound wave with a frequency of 25.0 kHz and a wavelength of 0.0136 metres.

Calculate the speed of this sound wave. [3 marks]

Wavespeed (m/s) = frquency (Hz) x wavelength (m)

v = fλ

You need to change the frequency from kilohertz to hertz.... make sure you know your SI Prefixes!

v = 25,000 x 0.0136 = 340 m/s

(e) Sound waves are longitudinal.

Describe a longitudinal sound wave. [2 marks]

The vibration of the air particles that the sound wave travels through is parallel to the direction of travel of the sound energy.This causes areas of compression and rarefaction of the air.

Note the question is asking not just about a longitudinal wave - but also a sound wave - you need to describe what happens to the air density as the sound passes through it to get that second mark!

(Total: 9 marks)