Radiation & Surface Colour
Physics: AQA GCSE Higher, topic 6.6.2
Radiation & Surface Colour
Surfaces can either reflect, absorb (take in), or emit (give out) infra-red radiation. Good absorbers (taker inners) of infra-red radiation are usually bad reflectors of infra-red radiation.
White surfaces
- White surfaces are good reflectors of infra-red radiation.
- White surfaces are poor emitters and absorbers of infra-red radiation.
Black surfaces
- Black surfaces are good emitters, good absorbers and poor reflectors.
Shiny surfaces
- Shiny surfaces of a colour are poorer absorbers of radiation than dull surfaces of the same colour.
- Shiny surfaces are poorer emitters and better reflectors than dull surfaces of the same colour.
A perfect black body
- A perfect black body is an object that absorbs all of the radiation incident on it.
- A black body does not reflect or transmit any radiation.
- Since a good absorber is also a good emitter, a perfect black body would be the best possible emitter.
Test yourself on Radiation & Surface Colour
Which of these surfaces is likely to be the best emitter of radiation?
Which of the following are true of emitters, absorbers, and reflectors?
Space blankets are designed to keep runners warm after marathons. They are shiny on both sides. Suggest why the shiny sides may help keep runners warm.
Oven trays and dishes are normally black and saucepans are usually shiny. Suggest reasons for this.