A thermal engineer is testing materials for a spacecraft's radiator panel. Two identical aluminium plates are prepared: Plate A is coated with a matte black thermal control paint, and Plate B is highly polished to a mirror-like finish. Both plates are electrically heated from behind so they are maintained at a constant, uniform temperature of 350 K350\text{ K}350 K in a vacuum chamber. An infrared radiometer is placed at an equal distance from the front face of each plate.
Despite both plates being at the exact same temperature, the radiometer measures a significantly higher intensity of infrared radiation from Plate A than from Plate B.
Explain why the radiometer records a higher reading for Plate A.
7 exam-style questions on Edexcel GCSE Physics 5.3 Black body radiation, covering 5.3.1 Emission of radiation and temperature, 5.3.2 Radiation balance and constant temperature, and 5.3.3 The temperature of the Earth. Each one has a worked solution and a mark scheme showing where the marks go.