Beer's Law relates the
absorbance of a substance at a given
wavelength of
light to its
concentration in solution. Beer's Law is defined by the following relation:
A=εb[C]
where A is the absorbance of the test solution, b is the path length of the sample, and [C] is the concentration of the light-absorbing material in the sample. ε is the molar absorbtivity, typically specified in units of (L/(mol•cm)). Using this relation, and knowing the molar absorbtivity of a substance at a given wavelength, the concentration of the substance in an unknown can be accurately determined.
Freshmen in chemistry have less trouble remembering the name of Beer's Law than they do Boyle's Law, the Heisenberg Uncertainty Principle, or the DeBroglie equation.