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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:
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);
In acoustics, Stokes's law of sound attenuation is a formula for the attenuation of sound in a Newtonian fluid, such as water or air, due to the fluid's viscosity.It states that the amplitude of a plane wave decreases exponentially with distance traveled, at a rate α given by = where η is the dynamic viscosity coefficient of the fluid, ω is the sound's angular frequency, ρ is the fluid ...
In physics, the attenuation length or absorption length is the distance λ into a material when the probability has dropped to 1/e that a particle has not been absorbed. Alternatively, if there is a beam of particles incident on the material, the attenuation length is the distance where the intensity of the beam has dropped to 1/ e , or about ...
Ultrasound attenuation can be used for extensional rheology measurement. There are acoustic rheometers that employ Stokes' law for measuring extensional viscosity and volume viscosity. Wave equations which take acoustic attenuation into account can be written on a fractional derivative form. [4]
The quantity nσ λ is known as the absorption coefficient (β a), a measure of attenuation with units of [cm −1]. The absorption coefficient is fundamentally the product of a quantity of absorbers per unit volume, [cm −3 ], times an efficiency of absorption (area/absorber, [cm 2 ]).
By recording the attenuation of light for various wavelengths, an absorption spectrum can be obtained. 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). [1]
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.