Radiation
Science Practicals: GCSE, topic 3.1.12
Radiation
Infra-red radiation can transfer thermal energy without a medium (substance to travel through).
Electromagnetic wave
- Infra-red radiation is an electromagnetic wave (it is part of the electromagnetic spectrum).
- We cannot see it but we do feel it as heat.
The Sun
- The infra-red radiation emitted by the Sun transmits thermal (heat) energy to the Earth.
- Infra-red radiation does not need a medium, so can still travel through space.
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 surfacers are poorer emitters and better reflectors than dull surfaces of the same colour.
Test yourself on Radiation
How can we detect infra-red radiation?
Which of the following statements are true of infra-red radiation?
Why does the Sun make us feel warm?
Which of these surfaces is likely to be the best emitter of radiation?
Which of the following are true of emitters, absorbers, and reflectors?