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
.

Notes:

- 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.

Source:

PAC, 2007, *79*, 293*
(Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006))
* on page 409