| Bodies that emit less thermal radiation than a
blackbody have surface
emissivities e less than 1. If the
surface emissivity is independent of wavelength, then the body is
called a "gray" body, in that no particular wavelength (or color) is
favored.
The net heat transfer from a small gray body at absolute
temperature T with surface emissivity e to a much larger enclosing gray (or black) body
at absolute temperature Te is given by, | 
has units of Watts, A is the total
radiating area of the blackbody, and s is
the 
