radiant intensity, \(I\)

Also contains definition of: intensity
@[email protected], \(P\), at all wavelengths per solid @[email protected], \(\varOmega\). The @[email protected] 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 @[email protected] of the cone. SI unit is \(\text{W sr}^{-1}\).
  1. Mathematical definition: \(I = \text{d}P/\text{d}\varOmega\). If the @[email protected] is constant over the solid @[email protected] considered, \(I = P/\varOmega\).
  2. Equivalent to \(I = \int_{\lambda}I_{\lambda}\, \text{d}\lambda\), where \(I_{\lambda}\) is the @[email protected] at @[email protected] \(\lambda\).
  3. It is not recommended to abbreviate this term to just intensity because it is confusing.
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 410 [Terms] [Paper]