Transmission of heat by radiation does not require any material medium. We can get both heat and light from the sun by radiation. In between the earth and the sun there is no medium.
Definition: Heat radiation is the process by which heat travels from one place to another place without the help of any material medium. If the medium is in the path, its temperature will not be changed. The energy which is transmitted by radiation is called radiant heat.
Radiant heat energy has the following characteristics:
- Radiant heat energy can travel through vacuum.
- If travels in straight line and with the velocity of light (3X108ms-1).
- Radiant heat energy obeys inverse square law.
- It obeys the laws of reflection and reflection of light.
- Just like light it is diffused.
- It demonstrates the phenomena of diffraction, interference and polarization.
- The amount of radiant energy is not influenced by the presence of surrounding objects.
- It does not change the temperature of the medium, through which it passes.