Introduction to Modern Physics
Radiation is a photon emission that occurs when electrons change orbit. Thermal radiation occurs when the excitation is caused by heating. A blackbody is an ideal radiator that absorbs all incident radiation regardless of wavelength and direction.
Blackbody emissive power: the radiation emitted by a blackbody per unit time and per unit surface area.
Spectral blackbody emissive power: the amount of radiation energy emitted by a blackbody per unit surface area and per unit wavelength about the wave length. The following relationship between emissive power, temperature and wavelength is known as Plank’s distribution law.
Blackbody radiation function: the fraction of radiation emitted from blackbody at temperature, T in the wavelength band.
Radiation Properties of Real Surfaces:
The thermal radiation emitted by a real surface is a function of surface temperature, T , wavelength, direction and surface properties.