spectral quantities

https://doi.org/10.1351/goldbook.S05823
Quantities characterizing electromagnetic radiation (@[email protected], energy, energy density, intensity, @[email protected], @[email protected], irradiance, etc.) derived by differentiation with respect to @[email protected], frequency or wavenumber, e.g. spectral (concentration of) irradiance is the derivative of the irradiance with respect to @[email protected] (\(E_{\lambda }\)), frequency (\(E_{\nu }\)) or wavenumber (\(E_{\stackrel{˜}{\nu }}\)).
Source:
Green Book, 2nd ed., p. 31 [Terms] [Book]