| quotient of the spectral radiant flux absorbed between the internal entry and exit surfaces of the layer and the spectral flux that enters into the layer after crossing the entry surface Note 1 to entry: For a given layer the spectral internal absorptance depends on the path length of the radiation in the layer, and hence, in particular, on the angle of incidence. Note 2 to entry: The spectral internal absorptance has unit one. Note 3 to entry: This entry was numbered 845-04-82 in IEC 60050-845:1987.
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