Absorption

This is property of material to convert the radiation they receive (such as light) into different forms of energy, mostly heat. A measure of this property is the degree of absorption a = F_a / F, the ratio of the luminous flux absorbed to the incident luminous flux. (Reflection, Transmittance).

a = Fa / F F  = incident luminous flux Fa = absorbed luminous flux Fr = reflected luminous flux Ft = transmitted luminous flux

Reflection, Absorption and Transmission in schematic format