The attenuation of light on passage through a solid or liquid may be quantified by reference to Beer’s (or Beer Lambert) Law. Given an input light intensity Io and transmitted intensity It and a path length L, the product of light absorption and light scattering A is accurately predicted by the linearization formula:-
A = Log10 (lo/ It) = e.l.c
Where c is the colorant concentration (if any) and e the absorption intensity (or molar extinction coefficient) and l is the path length.