![]() The absorbance of an object quantifies how much of the incident light is absorbed by it (instead of being reflected or refracted). Which among them practitioners use varies by field and technique, often due simply to the convention. Related measures, including absorbance (also called "optical density") and optical depth (also called "optical thickness")Īll these quantities measure, at least to some extent, how well a medium absorbs radiation.Other measures of radiation absorption, including penetration depth and skin effect, propagation constant, attenuation constant, phase constant, and complex wavenumber, complex refractive index and extinction coefficient, complex dielectric constant, electrical resistivity and conductivity."Extinction" in astronomy, which is equivalent to the attenuation coefficient.The absorption cross section and scattering cross-section, related closely to the absorption and attenuation coefficients, respectively.The mass attenuation coefficient (also called "mass extinction coefficient"), which is the absorption coefficient divided by density.The Molar attenuation coefficient (also called "molar absorptivity"), which is the absorption coefficient divided by molarity (see also Beer–Lambert law).The attenuation coefficient (NB used infrequently with meaning synonymous with "absorption coefficient"). ![]() The absorption coefficient along with some closely related derived quantities.Many approaches can potentially quantify radiation absorption, with key examples following. Main article: Mathematical descriptions of opacity Ī notable effect of the absorption of electromagnetic radiation is attenuation of the radiation attenuation is the gradual reduction of the intensity of light waves as they propagate through the medium.Īlthough the absorption of waves does not usually depend on their intensity (linear absorption), in certain conditions ( optics) the medium's transparency changes by a factor that varies as a function of wave intensity, and saturable absorption (or nonlinear absorption) occurs. In physics, absorption of electromagnetic radiation is how matter (typically electrons bound in atoms) takes up a photon's energy - and so transforms electromagnetic energy into internal energy of the absorber (for example, thermal energy). ![]() By recording the attenuation of light for various wavelengths, an absorption spectrum can be obtained. Other photons are scattered (not shown here) or transmitted unaffected if the radiation is in the visible region (400–700 nm), the transmitted light appears as the complementary color (here red). Upon striking the sample, photons that match the energy gap of the molecules present (green light in this example) are absorbed, exciting the molecules. A white light source - emitting light of multiple wavelengths - is focused on a sample (the pairs of complementary colors are indicated by the yellow dotted lines). This example shows the general principle using visible light as a specific example. ( November 2010) ( Learn how and when to remove this template message)Īn overview of absorption of electromagnetic radiation. Please help to improve this article by introducing more precise citations. This article includes a list of general references, but it lacks sufficient corresponding inline citations.
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