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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 absorption coefficient for spectral flux (a beam of radiation with a single wavelength, [W/m 2 /μm]) differs from the absorption coefficient for spectral intensity [W/sr/m 2 /μm] used in Schwarzschild's equation. Integration of an absorption coefficient over a path from s 1 and s 2 affords the optical thickness (τ) of that path, a ...
Variable pathlength absorption spectroscopy uses a determined slope to calculate concentration. As stated above this is a product of the molar absorptivity and the concentration. Since the actual absorbance value is taken at many data points at equal intervals, background subtraction is generally unnecessary.
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. Other applications appear in physical optics , where it quantifies astronomical extinction and the absorption of photons , neutrons , or rarefied gases .
Radiative transfer (also called radiation transport) is the physical phenomenon of energy transfer in the form of electromagnetic radiation. The propagation of radiation through a medium is affected by absorption, emission, and scattering processes. The equation of radiative transfer describes these interactions mathematically. Equations of ...
The radiative absorption of clouds is also dependent on the liquid water path. An increase of liquid water path leads to an increase in absorption. Again, the largest increase is seen with lower levels of liquid water path. [4] These connections are due to the proportionality between the liquid water path and the optical depth of the cloud. [5]
Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". [1] Alternatively, for samples which scatter light, absorbance may be defined as "the negative logarithm of one minus absorptance, as measured on a uniform sample". [2]
where p A is the partial pressure of A over the surface, [S] is the concentration of free sites in number/m 2, [A ad] is the surface concentration of A in molecules/m 2 (concentration of occupied sites), and k ad and k d are constants of forward adsorption reaction and backward desorption reaction in the above reactions.