GCSE Physics · AQA 8463 · Topic 4.6.3
Black body radiation
Key points
- All bodies emit and absorb infrared radiation, whatever their temperature. The hotter the body, the more radiation it emits each second and the shorter the peak wavelength.
- A perfect black body absorbs all radiation that hits it and is also the best possible emitter.
- An object at constant temperature absorbs radiation at the same rate as it emits it. If it absorbs faster than it emits, its temperature rises.
- Earth's temperature depends on the balance between radiation absorbed from the Sun and radiation emitted into space. Greenhouse gases absorb some emitted radiation.
- Required practical (all GCSE physics): investigate how the colour and texture of a surface affect infrared emission, for example with a Leslie cube. Matt black surfaces emit best.
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Everything around you, including you, is giving out infrared radiation all the time. How much an object emits and absorbs decides whether it warms up, cools down or stays at a steady temperature, and the same balance controls the…
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