[2.13.8.4] ε(λ,T ) (of an element of surface of an opaque temperature radiator that has an optical smooth surface)
The ratio of its spectral radiant exitance to that of a blackbody at the same temperature:
Note: Hemispherical emissivity is frequently called “total” emissivity. “Total” by itself is ambiguous and should be avoided since it may also refer to “spectral-total” (all wavelengths) as well as “directional-total” (all directions). (See Section 2.13.8.2, spectral-total hemispherical emissivity.)
« Back to Definitions Index