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The attenuation coefficient of a volume, denoted μ, is defined as [6] =, where Φ e is the radiant flux;; z is the path length of the beam.; Note that for an attenuation coefficient which does not vary with z, this equation is solved along a line from =0 to as:
Attenuation is linearly dependent on the medium length and attenuation coefficient, as well as – approximately – the frequency of the incident ultrasound beam for biological tissue (while for simpler media, such as air, the relationship is quadratic). Attenuation coefficients vary widely for different media.
absorption coefficient is essentially (but not quite always) synonymous with attenuation coefficient; see attenuation coefficient for details; molar absorption coefficient or molar extinction coefficient , also called molar absorptivity , is the attenuation coefficient divided by molarity (and usually multiplied by ln(10), i.e., decadic); see ...
Mass attenuation coefficients of selected elements for X-ray photons with energies up to 250 keV. The mass attenuation coefficient, or mass narrow beam attenuation coefficient of a material is the attenuation coefficient normalized by the density of the material; that is, the attenuation per unit mass (rather than per unit of distance).
In telecommunications, the term attenuation constant, also called attenuation parameter or attenuation coefficient, is the attenuation of an electromagnetic wave propagating through a medium per unit distance from the source. It is the real part of the propagation constant and is measured in nepers per metre.
In chemistry, the molar absorption coefficient or molar attenuation coefficient (ε) [1] is a measurement of how strongly a chemical species absorbs, and thereby attenuates, light at a given wavelength. It is an intrinsic property of the species.
Optical depth of a material is also related to its attenuation coefficient by: = (), where l is the thickness of that material through which the light travels; α ( z ) is the attenuation coefficient or Napierian attenuation coefficient of that material at z ,
where μ is the linear attenuation coefficient, μ/ρ is the mass attenuation coefficient and ρ is the density of the material. The mass attenuation coefficient can be looked up or calculated for any material and energy combination using the National Institute of Standards and Technology (NIST) databases. [7] [8]