https://doi.org/10.1351/goldbook.R05045
Radiant power, \(P\), at all wavelengths per solid angle, \(\varOmega\). The @R05046-2@ emitted in a given direction by a source or an element of the source in a small cone containing the given direction divided by the solid angle of the cone. SI unit is \(\rm{W sr}^{-1}\).
Notes:
- Mathematical definition: \(I = \rm{d}P/\rm{d}\varOmega\). If the radiant power is constant over the solid angle considered, \(I = P/\varOmega\).
- Equivalent to \(I = \int_{\lambda}I_{\lambda}\, \rm{d}\lambda\), where \(I_{\lambda}\) is the spectral radiant intensity at wavelength \(\lambda\).
- It is not recommended to abbreviate this term to just intensity because it is confusing.