quotient of absorbed radiant flux, Φa, and incident radiant flux, Φm

Note 1 to entry: The absorptance is also defined spectrally in terms of wavelength, in which case, "spectral" is added before the quantity name.

Note 2 to entry: Due to energy conservation, α + ρ + τ = 1 except when polarized radiation is observed, where ρ is reflectance and τ is transmittance.

Note 3 to entry: The absorptance has unit one.

Note 4 to entry: This entry was numbered 845-04-75 in IEC 60050-845:1987.

Note 5 to entry: This entry was numbered 17-5 in CIE S 017:2011.

Publication date: 2020-12
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