In
physics
Physics is the natural science that studies matter, its 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 which r ...
, the attenuation length or absorption length is the
distance
Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). ...
into a material when the
probability
Probability is the branch of mathematics concerning numerical descriptions of how likely an Event (probability theory), event is to occur, or how likely it is that a proposition is true. The probability of an event is a number between 0 and ...
has dropped to
that a
particle
In the physical sciences, a particle (or corpuscule 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 ...
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
, or about 63% of the particles have been stopped.
Mathematically, the probability of finding a particle at depth ''x'' into the material is calculated by
Beer–Lambert law
The Beer–Lambert law, also known as Beer's law, the Lambert–Beer law, or the Beer–Lambert–Bouguer law relates the attenuation of light to the properties of the material through which the light is travelling. The law is commonly applied t ...
:
:
.
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 valu ...
*
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 att ...
*
Radiation length In physics, the radiation length is a characteristic of a material, related to the energy loss of high energy particles electromagnetically interacting with it.
Definition
In materials of high atomic number (e.g. W, U, Pu) the electrons of energie ...
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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