what is radiation?
- continual emission of infrared waves from the surface of all bodies, transmitted without the aid of a medium.
- does not require a medium , and can even take place in a vacuum.

- all objects emit some radient heat
-the sun is a major source of radient heat
it emits electromagnetic waves to make us feel warm ---> infrared waves




factors affecting the rate of radiation

A. colour and texture of the surface
~ dull, black surfaces are better absorbers and emitters of infrared radiation than shiny, white surfaces



absorption of radiation:
dull black surfaces absorb radiation faster(so it will be hotter) than white and bright surfaces.
(note the temperature difference on the thermometer)


emission of radiation:
dull black surfaces radiate more heat faster than white shiny surfaces.
(again, note the temperature difference)







B. surface temperature
~ the higher the temperature, the higher the rate of radiation





~ the colder the object, the higher the rate of heat absorption





C. surface area
~ the larger the surface area, the higher the rate of radiation