Absorbance
A dimensionless quantity denoted by A, used to measure the absorption of electromagnetic radiation, e.g. light, by matter.
It is defined by the Beer-Lambert Law :
where I0 is the intensity of the incident beam of light of wavelength n , I is the intensity of the beam which has passed through the sample or solution of pathlength l containing a substance characterised by a molar absorption (extinction) coefficient e and with a concentration c.
