radiant exitance, M

Radiant power, P, emitted at all wavelengths by an element of surface containing the source point under consideration divided by the area of the source. SI unit is W m −2.
  1. Mathematical definition: M = d P / d S. If the radiant powerP is constant over the surface area considered, M = P / S.
  2. Equivalent to the integration of the radiant power leaving a source over the solid angle and over the whole wavelength range. Mathematical definition: M = ∫ λ M λ ⁢ d λ, where M λ is the spectral radiant exitance at wavelengthλ.
  3. Same as spherical radiant exitance. Formerly called radiant emittance.
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 409