Thermal radiation

Thermal radiation is the emission of electromagnetic radiation (waves) generated by the thermal motion of particles in the matter (that has a temperature greater than absolute zero). It represents the conversion of thermal energy into electromagnetic energy. Particle motion results in charge-acceleration or dipole oscillation which produces electromagnetic radiation.

The characteristics of thermal radiation depend on various properties of the surface it is emanating from, including its temperature, spectral absorptivity, and spectral emissive power, as expressed by Kirchhoff’s law.