Radiant power, , 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 .
- Mathematical definition: . If the radiant power is constant over the surface area considered, .
- Equivalent to the integration of the radiant power leaving a source over the solid angle and over the whole wavelength range. Mathematical definition: , where is the spectral radiant exitance at wavelength.
- 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