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The absorption coefficient of a volume, denoted μ a, and the scattering coefficient of a volume, denoted μ s, are defined the same way as the attenuation coefficient. [6] The attenuation coefficient of a volume is the sum of absorption coefficient and scattering coefficients: [6]
In 1957 John Philip introduced the term sorptivity and defined it as a measure of the capacity of the medium to absorb or desorb liquid by capillarity. [1]According to C Hall and W D Hoff, the sorptivity expresses the tendency of a material to absorb and transmit water and other liquids by capillarity.
There is a fundamental relationship (Gustav Kirchhoff's 1859 law of thermal radiation) that equates the emissivity of a surface with its absorption of incident radiation (the "absorptivity" of a surface). Kirchhoff's law is rigorously applicable with regard to the spectral directional definitions of emissivity and absorptivity.
A reverberation chamber is used to test the sound absorption coefficients and NRC of a material. The noise reduction coefficient (commonly abbreviated NRC) is a single number value ranging from 0.0 to 1.0 that describes the average sound absorption performance of a material. An NRC of 0.0 indicates the object does not attenuate mid-frequency ...
In the context of ozone shielding of ultraviolet light, absorption cross section is the ability of a molecule to absorb a photon of a particular wavelength and polarization. Analogously, in the context of nuclear engineering , it refers to the probability of a particle (usually a neutron ) being absorbed by a nucleus.
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).
This is calculated using its dimensions and the absorption coefficients of the walls. [4] The total absorption is expressed in Sabins and is useful in, for instance, determining the reverberation time of auditoria. Absorption coefficients can be measured using a reverberation room, which is the opposite of an anechoic chamber (see below).
The SI unit of molar absorption coefficient is the square metre per mole (m 2 /mol), but in practice, quantities are usually expressed in terms of M −1 ⋅cm −1 or L⋅mol −1 ⋅cm −1 (the latter two units are both equal to 0.1 m 2 /mol).