| Definition: | relative decrease in radiant flux caused by absorption and scattering, expressed by the relative density of the spectral radiant flux, Φe,λ(λ), with respect to propagation length, l, of a collimated beam at a point in an absorbing and scattering medium Note 1 to entry: The spectral linear attenuation coefficient is expressed in metre to the power minus one (m−1). Note 2 to entry: This entry was numbered 845-04-76 in IEC 60050-845:1987.
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