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The extinction law's primary application is in chemical analysis, where it underlies the Beer–Lambert law, commonly called Beer's law. Beer's law states that a beam of visible light passing through a chemical solution of fixed geometry experiences absorption proportional to the solute concentration .
The absorbance of a material that has only one absorbing species also depends on the pathlength and the concentration of the species, according to the Beer–Lambert law =, where ε is the molar absorption coefficient of that material; c is the molar concentration of those species; ℓ is the path length.
The Beer–Lambert law states that there is a logarithmic dependence between the transmission (or transmissivity), T, of light through a substance and the product of the absorption coefficient of the substance, α, and the distance the light travels through the material (i.e. the path length), ℓ.
An electromagnetic wave propagating in the +z-direction is conventionally described by the equation: (,) = [()], where E 0 is a vector in the x-y plane, with the units of an electric field (the vector is in general a complex vector, to allow for all possible polarizations and phases);
The difference in intensity is directly proportional to the concentration of the analyte in the sample, following the Beer-Lambert law: * **A = εcl**, where: * A is the absorbance measured. * ε is the molar absorptivity (constant specific to the element and wavelength). * c is the concentration of the analyte.
This may be related to other properties of the object through the Beer–Lambert law. Precise measurements of the absorbance at many wavelengths allow the identification of a substance via absorption spectroscopy, where a sample is illuminated from one side, and the intensity of the light that exits from the sample in every direction is measured.
Created Date: 8/30/2012 4:52:52 PM
The absorbance can be written as sum of absorbances of each species (Beer–Lambert law) = = (), where the concentration of species i, the optical path length. By definition, an isosbestic point can be interpreted as a fixed linear combination of species concentrations, L = ∑ i n b i c i , d L d t = 0 , {\displaystyle L=\sum _{i}^{n}b_{i}c_{i ...