Absorbance is a quantitative measure expressed as a logarithmic ratio between the radiation falling upon a material and the radiation transmitted through a material.Absorbance measurements are often carried out in analytical chemistry.
In physics, the term spectral absorbance is used interchangeably with spectral absorptance or absorptivity. In this case it has a slightly different meaning: the fraction of radiation absorbed at specific wavelengths.

Related formulas


A_λAbsorbance (dimensionless)
I1Imtensity of the transmitted radiation (W/m2)
I0Intensity of the incident radiation (W/m2)