Radiation is that method of heat transfer which does not require any material medium.
In this process heat energy is transferred in the form of electro-magnetic waves. The properties of radiation are similar to those of light.
- It travels with the velocity of light (3 x 108 m s-1 in vacuum).
- It shows all the properties of light, i.e. reflection, interference, polarization etc.
- It obeys inverse square law.