ABSTRACT
It is well accepted that electromagnetic energy may be absorbed or reflected, or both simultaneously, upon its incidence on a material body. When the material body is in thermodynamic equilibrium with its environment, the material absorbs and radiates energy at the same rate. If the material reflects nothing and instead absorbs all of the incident radiation, then the material is called a black body. The black body radiation is well explained by Max Planck on the basis of quantum theory. But in practice, all the bodies are not really black. Accordingly, the real body spectrum at the same black body temperature may be compared with the black body spectrum. The real body radiation spectrum depends on polarization, angular variation of the emitted radiation, absorption, and scattering, which in turn are governed by the geometrical configuration of the surface and interior of the medium concerned, and also by the spatial distribution of its dielectric properties and temperature.
