A laboratory uses an infrared calibration target that behaves as a perfect black body. All four surfaces, including the target, have the same emitting surface area and are maintained at the same temperature.
The energy emitted as radiation by each surface in 20 seconds is shown in the table.
| Surface | Energy emitted in 20 seconds in J |
|---|---|
| Perfect black body target | 240 |
| Plate P | 190 |
| Plate Q | 240 |
| Plate R | 265 |
Which statement about the results is correct?
The result for plate Q cannot be correct because no surface can emit at the same rate as a perfect black body.
The result for plate P cannot be correct because surfaces at the same temperature must emit equal amounts of radiation.
The result for the target cannot be correct because a perfect black body absorbs radiation instead of emitting it.
The result for plate R cannot be correct because it emitted more energy than the target.
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.