Infrared

3 marks · Normal

Special cameras designed to detect infrared waves can be used to find people in darkness, such as in a rescue operation after a building collapse. Infrared images show hot bodies as white shapes against a dark background.

(a)

Explain why infrared cameras are useful for finding people in such situations.

[3 marks]

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(a) — · must show Human bodies are warmer than surroundings and emit more infrared, Infrared cameras can detect this emission, People stand out against cooler objects, even in darkness

Must show: Human bodies emit infrared (even in darkness), Infrared cameras detect heat, Contrast with cold surroundings enables detection

Common mistakes: Confusing visible with infrared; Not stating heat difference

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Marking points

B1 (a) · 1 mark · States human bodies emit more infrared than surroundings.

B2 (a) · 1 mark · Explains cameras detect heat (infrared) not visible light.

B3 (a) · 1 mark · States people appear as bright shapes against a cooler background, so can be found in darkness.

Worked solution

Humans are warmer and emit more infrared radiation than rubble or surroundings. Infrared cameras detect this thermal radiation, so people appear as bright shapes even when there is no visible light. This makes it possible to find people in total darkness.