AQA · GCSE Physics

Harvest Moon: light and colour GCSE challenge

Can you explain an orange Moon using school physics? Try this original eight-mark challenge about visible light, scattering and a colour filter.

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Question

8 marks

Answer all parts. No calculation is required.

1(a)

The Moon reflects sunlight towards Earth. Consider red and blue light travelling from the Moon through a vacuum. Compare their wavelengths and their speeds.

[2 marks]

1(b)

Molecules in air scatter blue light out of a direct beam more strongly than red light. Explain why the Moon can look orange when it is near the horizon but much paler when it is high in the sky. The lunar surface has not changed.

[3 marks]

1(c)

A pupil photographs the orange Moon through a blue filter. Most of the light reaching the filter is red or orange, with only a small blue component. An ideal blue filter transmits blue light and absorbs the other visible colours. The pupil predicts that the filter will make a bright blue image by changing the red and orange light into blue light. Explain why the prediction is wrong and describe the image expected with the same camera exposure.

[3 marks]

Start the question to write your answer, receive marks and ask Sherlock Ohms for text help.