A thermal sensor is suspended in a vacuum chamber. Energy is transferred to and from the sensor only by radiation. The sensor is initially at constant temperature while infrared radiation from a heater reaches it through an opening. A shutter partly covers the opening, reducing the infrared radiation reaching the sensor.
Which statement explains why the sensor begins to cool?
Its absorption rate decreases while its emission rate is initially unchanged, so the sensor loses energy overall.
Its absorption rate decreases below its emission rate, so the sensor gains energy overall.
Its absorption and emission rates both decrease by the same amount, so the sensor loses energy overall.
Its emission rate increases because less radiation reaches it, so the sensor loses energy overall.
106 exam-style questions on AQA GCSE Physics 6.3 Black body radiation, covering 6.3.1 Emission and absorption of infrared radiation and 6.3.2 Perfect black bodies and radiation. Each one has a worked solution and a mark scheme showing where the marks go.