Note 1 to entry: The unit of the quantity length has to be specified. If a new unit of length is used that is k times the magnitude of the original one, then the value of ${\alpha }_{\text{i}\text{,o}}^{}(\lambda )=1-{\tau }_{\text{i}\text{,o}}(\lambda )$ will change to ${{\alpha }^{\prime }}_{\text{i}\text{,o}}^{}(\lambda )=1-{[{\tau }_{\text{i}\text{,o}}(\lambda )]}^k$.

Note 2 to entry: The spectral absorptivity has unit one.

Note 3 to entry: This entry was numbered 845-04-88 in IEC 60050-845:1987.