Beer law is also known as Beer-Lambert law. Beer law is the equation that relates attenuation of the light to the properties of a particular material.  The beer law states that the chemical concentration is directly proportional to solution absorbed. This relationship is used to decide the chemical species concentration in a specified solution with the use a spectrophotometer. Beer law is written as A=έbc. Where  A is the absorbance, έ is the molar absorptivity, b is the path length of a sample and c is a concentration of a compound solution. When calculating the absorbance, you have to consider the following assumptions. The first assumption is that the absorbance is directly proportional to a path length of a particular sample which can be expressed as A άc(1.1) Aάc and the second assumption is that the absorbance is directly proportional to the concentration of a particular sample it is expressed as Aά1(1.3)(1.3)Aά1.  Though the comparison of the blank cuvette with a sample is the most common method used in beer’s law calculation, you can also prepare a graph using the standard solutions to decide a concentration of a particular specimen. The proportion of light absorbed depends on how many molecules it interacts with. The absorbance of the solution varies as the concentration or size of the container varies.  The values of the molar absorptivity vary hugely. Beer law is limited by both chemical and instrumental factors, which include a scattering of lights, the fluorescence of the sample, the change in the refractive index at the high analyte concentration, stray lights,  shift in the chemical equilibria and non-monochromatic radiation.

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