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P1 6.1c – Student worksheet
Going supersonic
1
Describe what is meant by the Doppler effect, using sound as a model. (3 marks)
2
An astronomer is looking at a star. He is interested in what elements there are in the star. He
sees the spectral pattern for helium, but notices that it has moved slightly towards the blue end
of the visible spectrum. Explain what he should conclude from this observation. (4 marks)
3
Aeroplanes can fly faster than sound. Use the Doppler effect to explain why pilots are not
allowed to fly faster than sound over land. (3 marks)
4
Discuss whether it’s possible to break the light barrier. What might you see? (3 marks)
P1 6.1d – Student worksheet
Understanding the Doppler effect
Look at the animation of the Doppler effect. This is a Java applet that demonstrates the Doppler
effect.
1
What happens when the object is stationary? (1 mark)
2
If the object is moving very slowly (speed = 0.01), is there a noticeable effect? Explain your
answer. (2 marks)
3
What is meant by the Mach number shown in the yellow box? (1 mark)
4
The Mach number is set at 0.2. How fast is that in m/s? (2 marks)
5
Suggest something (other than an aeroplane) that can travel at Mach 0.2. (1 mark)
6
Explain whether there is a noticeable Doppler effect. (2 marks)
7
What happens if the Mach number is increased to 1? (1 mark)
8
A high speed aeroplane passes at a speed of Mach 1. What do you think you would hear as
the plane:
a
approached? (1 mark)
b
passed? (1 mark)
c
moved away? (1 mark)
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