Beer's law

In optics, the Beer-Lambert law, also known as Beer's law or the Lambert-Beer law or the Beer-Lambert-Bouguer law (in fact, most of the permutations of these three names appear somewhere in literature) is an empirical relationship that relates the absorption of light to the properties of the material through which the light is traveling.
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(A=abc or A= bc) Beer-Lambert law. In absorption spectroscopy , the absorbance of a dilute solution is equal to its absorptivity times the path length times the concentration of the absorbing solute.