spectral optical thickness, <of a medium>
spectral optical depth, <of a medium>
integral of the spectral linear attenuation coefficient,
Note 1 to entry: The spectral optical thickness is used in atmospheric physics and physical oceanography.
Note 2 to entry: The spectral optical thickness has unit one.
Note 3 to entry: This entry was numbered 845-04-80 in IEC 60050-845:1987.
Note 4 to entry: This entry was numbered 17-1226 and 17-1225 in CIE S 017:2011.