A laboratory is selecting a material for a calibration source used to check infrared thermometers. Two samples, P and Q, have equal surface areas and are maintained at the same temperature.
During the same time interval, 100 J of radiation is incident on each sample. The table shows what happens to the radiation.
| Sample | Radiation incident on the sample | Radiation absorbed | Radiation reflected | Radiation transmitted |
|---|---|---|---|---|
| P | 100 J | 100 J | 0 J | 0 J |
| Q | 100 J | 70 J | 20 J | 10 J |
State which sample behaves as a perfect black body. Explain your answer.
Compare the rate at which samples P and Q emit infrared radiation. Explain your answer.
Sample P is then heated to a much higher temperature. Explain how the radiation emitted by P changes and why P may be seen to glow.
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.