Beer's law

Beer's law [for August Beer], physical law stating that the quantity of light absorbed by a substance dissolved in a nonabsorbing solvent is directly proportional to the concentration of the substance and the path length of the light through the solution the law is sometimes also referred to as the Beer-Lambert law or the Bouguer-Beer law. Beer's law is commonly written in the form A cl, where A is the absorbance, c is the concentration in moles per liter, l is the path length in centimeters, and ε is a constant of proportionality known as the molar extinction coefficient. The law is accurate only for dilute solutions deviations from the law occur in concentrated solutions because of interactions between molecules of the solute, the substance dissolved in the solvent.

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