An astronomer is planning a survey of a cool dust cloud and wants to make a continuous record of its infrared radiation.
At the top of the Earth's atmosphere, the infrared radiation from the cloud gives a signal rate of 72 counts per minute72\ \mathrm{counts\ per\ minute}72 counts per minute in a detector. An orbiting observatory with this detector receives the full signal rate. An Earth-based observatory with the same detector receives only 0.25 of the signal rate at the top of the atmosphere.
Calculate the infrared signal rate received by the Earth-based observatory.
An orbiting observatory records infrared radiation for 2.0 h. Calculate how long an Earth-based observatory would need to record the same total infrared signal.
Explain why the orbiting observatory is more suitable for making the continuous infrared record.
75 exam-style questions on Edexcel GCSE Physics 7.3 Stars, covering 7.3.1 Evolution of stars similar to the Sun, 7.3.2 Evolution of massive stars, and 7.3.3 Observing the Universe. Each one has a worked solution and a mark scheme showing where the marks go.