radiation temperature

(T_r), a physical parameter characterizing the total (for all wavelengths) radiant emittance B_e of a radiating body. It is equal to the temperature of a black-body at which the blackbody’s emittance .

The laws of thermal radiation permit the expression to be written in the form , where ∊_T is the emissivity of the body, σ the Stefan-Boltzmann constant, and T the absolute temperature of the body. If the value of ∊_T is known and the temperature T_r has been measured (with a radiation pyrometer), it is possible to calculate the temperature of the body by the relation T = T_r∊_T^–¼ For thermal radiation of all bodies other than a blackbody, ∊_T < 1; therefore, T_r < T. In the case of luminescence, however, T_r may be greater than T.