The energy emitted by a body in the form of radiation on account of its temperature is called thermal radiation. It depends on,
(i) temperature of the body.
(ii) nature of the radiating body
The wavelength of thermal radiation ranges from 8 x 10-7 m to 4 x 10-4 m. They belong to infra-red region of the electromagnetic spectrum.
Properties of thermal radiations
- Thermal radiations can travel through vacuum.
- They travel along straight lines with the speed of light.
- They can be reflected and refracted. They exhibit the phenomenon of interference and diffraction.
- They do not heat the intervening medium through which they pass.
- They obey inverse square law.