ABSTRACT
Radiometry deals with radiant quantities and applies to the entire electromagnetic spectrum. Photometry is a subdivision of radiometry that deals only with the part of the spectrum perceived by the human eye as light. In radiometry it is possible to study nonvisible radiation but in photometry only the visible part of the spectrum is considered. Radiation heat transfer, as the name suggests, deals with heat exchange by exchange of radiation, with bodies absorbing its heat much as the eye absorbs light.
