Generalized equations for the calculation of absorptance, reflectance, and transmittance of a number of parallel surfaces.

Derivations of general equations to describe the absorptance, reflectance, and transmittance of any number of parallel surfaces are presented. Two corollaries describing the propagation of light by two surfaces are derived and then used to derive the general equations. These general equations have wide utility because they describe exactly the propagation of light by any number or type of parallel surfaces (interfaces), using relatively simple expressions, which are readily adaptable for digital computer use.