AQA ยท A level Physics

Rotational wave amplification A-level challenge

Can you get 100%? Use a laboratory analogue of rotating black-hole physics to test wave power, active modulation and conservation of energy.

Read about laboratory rotational super-radiance

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Question

7 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

A wave enters the ring with power 0.80 W and leaves with power 1.04 W. Calculate the percentage increase in wave power.

[3 marks]

1(b)

The components do not physically rotate. Instead, an electrical drive moves a pattern of changing resonant properties around the ring. Explain why the larger outgoing wave does not violate conservation of energy.

[2 marks]

1(c)

The experiment found that reversing the direction of the travelling modulation changed which rotational wave patterns were amplified. The outgoing power exceeded the incoming power only while the electrical modulation was switched on. Explain why these observations support energy transfer from synthetic rotation rather than ordinary passive reflection.

[2 marks]

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