https://doi.org/10.1351/goldbook.R05045
@[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 \(\text{W sr}^{-1}\).
Notes:
- Mathematical definition: \(I = \text{d}P/\text{d}\varOmega\). If the @[email protected] is constant over the solid @[email protected] considered, \(I = P/\varOmega\).
- Equivalent to \(I = \int_{\lambda}I_{\lambda}\, \text{d}\lambda\), where \(I_{\lambda}\) is the @[email protected] at @[email protected] \(\lambda\).
- It is not recommended to abbreviate this term to just intensity because it is confusing.