GCSE Questions - Waves
Q18. Look at this diagram of a water wave.
(a)
(i) What is the wavelength of this wave?
λ = 6.1 - 2.6 = 3.6 cm (using the 'red' lines on the diagram) 
OR
λ = 7.9 - 4.5 = 3.5 cm (using the 'blue' lines on the diagram)
[1 mark]
(ii) What is the amplitude of this wave?
A = 2.4 cm
[1 mark]
(iii) The wavelength of the wave is changed to 25cm. Two waves are produced each second.
Calculate the speed of the wave in m/s.
λ = 25 cm = 0.25 m
f = 2 Hz
speed = fλ
speed = 0.25 x 2 = 0.5 m/s
[4 marks]
(b) Water waves are transverse and sound waves are longitudinal.
(i) Describe how water particles move in a transverse water wave.
The water particles move 'up and down'/oscillate/vibrate at right angles to the direction of travel of the wave.
[1 mark]
(ii) Describe how air particles move in a longitudinal sound wave.
The aire particles move 'backwards and forwards'/oscillate/vibrate parallel to the direction of travel of the wave.
[1 mark]
(c) Visible light is part of the electromagnetic spectrum.
(i) Name a wave in the electromagnetic spectrum that has a longer wavelength than red light.
One of the following:
Radio / infra-red / microwave
[1 mark]
(ii) Name a wave in the electromagnetic spectrum that has a higher frequency than violet light.
One of the following:
Ultra-violet / X-rays / gamma-rays
[1 mark]
(iii) State two uses of gamma-rays.
Any two from:
Radiotherapy / treating cancer tumours/ killing cancer cells
Irradiating food / sterilisation of instruments / killing bacteria or (harmful) microorganisms
As a tracer / medical imaging
Scanning metals / non-destructive testing (NDT)
[2 marks]
(Total 12 marks)
About this site
The examiner allowed any answer in the range 3.4 cm to 3.6 cm, as it depended which part of the graph you used to work out your answer! Always mark on the graph - this makes checking your answer easier at the end of the examination, and lets the examiner know what you are doing.
