What is the value of ε in Beer-Lambert Law?

The value of ε (molar absorptivity coefficient) in the Beer-Lambert Law varies depending on the substance being analyzed and the wavelength of light used. It is typically determined experimentally and is expressed in units of L·mol⁻¹·cm⁻¹. For example, the value of ε for a particular dye at a specific wavelength would be different from that of a protein or a different chemical compound. The value is unique to both the substance and the chosen wavelength.