An opaque heat shield is tested in an evacuated chamber. A lamp directs radiation at the shield.
During the test, the pale surface of the shield becomes dark. The table shows the rates of energy transfer immediately before and immediately after the surface becomes dark.
| Surface of shield | Rate of incident radiation in watts | Rate of reflected radiation in watts | Rate of emitted radiation in watts |
|---|---|---|---|
| Pale | 600 | 420 | 180 |
| Dark | 600 | 180 | 180 |
Explain why the temperature of the shield starts to rise when its surface becomes dark. Use data from the table.
Explain how the rate at which the shield emits radiation changes until its temperature becomes constant. Assume that the rates of incident and reflected radiation remain unchanged.
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.