This key facts covers ⬛ What is a Black Body? within Black Body Radiation for GCSE Physics. Revise Black Body Radiation in Energy for GCSE Physics with 16 exam-style questions and 5 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 2 of 7 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
⬛ What is a Black Body?
Definition: A black body is a theoretical perfect absorber and perfect emitter of radiation.
- Perfect absorber: Absorbs ALL radiation that hits it (reflects none)
- Perfect emitter: Emits the maximum amount of radiation at every wavelength
- Called "black" because a perfect absorber appears black at room temperature
- Real objects approximate black bodies (e.g., soot, stars, planets)
Figure 1a: Three objects at 300 K, 1000 K and 6000 K — the hotter the object, the more radiation it emits and the shorter its peak wavelength.
Figure 1b: Good vs poor emitters — a matt black surface emits far more radiation than a shiny silver one at the same temperature.
Practice questions for Black Body Radiation
What is a perfect black body?
Explain how the radiation emitted by an object changes as its temperature increases.