RADIATION
*Radiation is the transfer of heat through space (or) matter by means other than conduction (or) convection.
*Radiation is a process in which energetic particles (or) energetic waves travel through a medium (or) space. There are two types of radiation, ionizing and non-ionizing.
1.ABSORPTIVITY
Fraction of incident radiation absorbed.
2.REFLECTIVITY
Fraction of incident radiation reflected.
3.TRAMSMITTIVITY
Fraction of incident radiation transmitted.
Kichhoff's Law
The law states that "At any temperature the ratio of total emissive power E to the total absorptivity is a constant for all substances which are in thermal equilibrium with envirionment".
PLANCK'S LAW
Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T.
SHAPE FACTOR
The shape factor may be defined as "The fraction of radiative energy that is diffused from one surface element and strikes the other surface directly with no intervening reflections.