In
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
, the attenuation length or absorption length is the distance into a material when the
probability
Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an e ...
has dropped to that a
particle
In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass.
They vary greatly in size or quantity, from s ...
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
Intensity may refer to:
In colloquial use
* Strength (disambiguation)
*Amplitude
* Level (disambiguation)
* Magnitude (disambiguation)
In physical sciences
Physics
*Intensity (physics), power per unit area (W/m2)
*Field strength of electric, m ...
of the beam has dropped to , or about 63% of the particles have been stopped.
Mathematically, the probability of finding a particle at depth into the material is calculated by the
Beer–Lambert law
The Beer–Bouguer–Lambert (BBL) extinction law is an empirical relationship describing the attenuation in intensity of a radiation beam passing through a macroscopically homogenous medium with which it interacts. Formally, it states that the ...
:
:
.
In general is material- and energy-dependent.
See also
*
Beer's Law
*
Mean free path
In physics, mean free path is the average distance over which a moving particle (such as an atom, a molecule, or a photon) travels before substantially changing its direction or energy (or, in a specific context, other properties), typically as a ...
*
Attenuation coefficient
The linear attenuation coefficient, attenuation coefficient, or narrow-beam attenuation coefficient characterizes how easily a volume of material can be penetrated by a beam of light, sound, particles, or other energy or matter. A coefficient val ...
*
Attenuation (electromagnetic radiation)
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable ...
*
Radiation length
In particle physics, the radiation length is a characteristic of a material, related to the energy loss of high energy elementary particle, particles electromagnetically interacting with it. It is defined as the mean length (in cm) into the mate ...
References
*
* https://web.archive.org/web/20050215215652/http://www.ct.infn.it/~rivel/Glossario/node2.html
External links
* http://henke.lbl.gov/optical_constants/atten2.html
Particle physics
Experimental particle physics
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