| Status: |
STD 2005/06/07 |
| Code: |
142 |
| Symbol: |
m |
| EQ label: |
LENGTH |
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| Quantities associated with this Unit |
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| Quantity: |
object distance
|
| Concept definition: |
For a centred optical system, distance [ISO 80000-3:2006, item 3-1.9] from a given object to the closest surface of the centred optical system. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-7:2008, item 7-59.a and item 7-59.1] |
| Supplemental references: |
|
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| Quantity: |
sound particle displacement
|
| Concept definition: |
Instantaneous displacement of a particle in a medium from what would be its position in the absence of sound waves. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-8:2007, item 8-10.a] |
| Supplemental references: |
|
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| Quantity: |
mean free path
|
| Concept definition: |
For a particle, the average distance between two successive collisions with other molecules. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-9:2009, item 9-44.a] |
| Supplemental references: |
|
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| Quantity: |
half-value thickness
|
| Concept definition: |
The thickness [ISO 80000-3:2006, item 3-1.4] of the attenuating layer that reduces the quantity of interest of a unidirectional beam to half of its initial value. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-54.a] |
| Supplemental references: |
|
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| Quantity: |
length
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| Concept definition: |
The length of the path travelled by light in vacuum during a time interval of 1 / 299 792 458 of a second.
SI base unit. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-3:2006, 3-1.a] |
| Supplemental references: |
[ISO 80000-1:2009, Table 1, "length"] |
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| Quantity: |
wavelength
|
| Concept definition: |
The distance in the direction of propagation of a sinusoidal wave between two successive points where at a given instant in time the phase differs by 2π (see [ISO 80000-3:2006, item 3-25, Remarks]). |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-3:2006, item 3-17.a] |
| Supplemental references: |
[ISO 80000-7:2008, item 7-3.a and item 7-3.2]; [ISO 80000-8:2007, item 8-5.a] |
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| Quantity: |
Bohr radius
|
| Concept definition: |
(4π ε0h2)/(mee2 where ε0 is the electric constant [IEC 80000-6:2008, item 6-14.1], h is the reduced Planck constant [IEC 80000-6:2008, item 10-6.2], me is the rest mass of an electron [ISO 80000-10:2009, item 10-2], and e is the elementary charge [ISO 80000-10:2009, item 10-5.1]; 0,529 177 208 5936 x 10-10 metre. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-7.a] |
| Supplemental references: |
|
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| Quantity: |
electron radius
|
| Concept definition: |
-e2/(4π ε0mec02) where e is the elementary charge [ISO 80000-10:2009, item 10-5.1], ε0 is the electric constant [IEC 80000-6:2008, item 6-14.1], me is the rest mass of an electron [ISO 80000-10:2009, item 10-2], and c0 is the speed of light in vacuum [ISO 80000-7:2008, item 7-4.1]. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-21.a] |
| Supplemental references: |
|
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| Quantity: |
Compton wavelength
|
| Concept definition: |
h/mc0, where h is the Planck constant [ISO 80000-10:2009, item 10-6.1], m is the rest mass [ISO 80000-10:2009, item 10-2] of a particle and c0 is the speed of light in vacuum [ISO 80000-7:2008, item 7-4.1]. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-22.a] |
| Supplemental references: |
|
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| Quantity: |
mean free path of phonons
|
| Concept definition: |
The mean free path [ISO 80000-10:2009, item 10-73] of phonons. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-16.a and item 12-16.1] |
| Supplemental references: |
|
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| Quantity: |
diffusion length
|
| Concept definition: |
The square root of D τ, where D is the diffusion coefficient [ISO 80000-9:2009, item 9-45] and τ is lifetime [ISO 80000-3:2006, item 3-7]. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-34.a] |
| Supplemental references: |
|
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| Quantity: |
mean linear range
|
| Concept definition: |
The mean total rectified path length [ISO 80000-3:2006, item 3-1.1] travelled by a particle in the course of slowing down to rest (or to some suitable cut-off energy) in a given substance under specified conditions averaged over a group of particles having the same initial energy [ISO 80000-5:2007, item 5-20.1]. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-58.a] |
| Supplemental references: |
|
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| Quantity: |
nuclear radius
|
| Concept definition: |
The conventional radius of the sphere in which the nuclear matter is included. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-19.a] |
| Supplemental references: |
|
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| Quantity: |
mean free path
|
| Concept definition: |
The average distance [ISO 80000-3:2006, item 3-1.9] that particles travel between two successive specified reactions or processes. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-73.a] |
| Supplemental references: |
|
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| Quantity: |
slowing-down length
|
| Concept definition: |
The square root of L2, where L2 is the slowing-down area [ISO 80000-10:2009, item 10-74.1]. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-75.a and item 10-75.1] |
| Supplemental references: |
|
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| Quantity: |
diffusion length
|
| Concept definition: |
The square root of L2, where L2 is the diffusion area [ISO 80000-10:2009, item 10-74.2]. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-75.a and item 10-75.2] |
| Supplemental references: |
|
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| Quantity: |
migration length
|
| Concept definition: |
The square root of M2, where M2 is the migration area [ISO 80000-10:2009, item 10-74.3]. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-10:2009, item 10-75.a and item 10-75.3] |
| Supplemental references: |
|
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| Quantity: |
lattice vector
|
| Concept definition: |
The translation vector that maps the crystal lattice on itself. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-1.a and item 12-1.1] |
| Supplemental references: |
|
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| Quantity: |
fundamental lattice vectors
|
| Concept definition: |
The fundamental translation vectors for the crystal lattice. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-1.a and item 12-1.2] |
| Supplemental references: |
|
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| Quantity: |
lattice plane spacing
|
| Concept definition: |
The distance between successive lattice planes. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-3.a] |
| Supplemental references: |
|
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| Quantity: |
Burgers vector
|
| Concept definition: |
The vector characterizing a dislocation, i.e. the closing vector in a Burgers circuit encircling a dislocation line. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-7.a] |
| Supplemental references: |
|
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| Quantity: |
coherence length
|
| Concept definition: |
The distance [ISO 80000-3:2006, item 3-1.9] in a superconductor over which the effect of a perturbation is appreciable. |
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| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-39.a and item 12-39.2] |
| Supplemental references: |
|
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| Quantity: |
image distance
|
| Concept definition: |
For a centred optical system, distance [ISO 80000-3:2006, item 3-1.9] from an image of the given object to the closest surface of the centred optical system. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-7:2008, item 7-59.a and item 7-59.2] |
| Supplemental references: |
|
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| Quantity: |
object focal distance
|
| Concept definition: |
For a centred optical system, distance [ISO 80000-3:2006, item 3-1.9] from the focal point at the object side to the closest surface of the centred optical system. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-7:2008, item 7-59.a and item 7-59.3] |
| Supplemental references: |
|
|
| Quantity: |
image focal distance
|
| Concept definition: |
For a centred optical system, distance [ISO 80000-3:2006, item 3-1.9] from the focal point at the image side to the closest surface of the centred optical system. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-7:2008, item 7-59.a and item 7-59.4] |
| Supplemental references: |
|
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| Quantity: |
mean free path of electrons
|
| Concept definition: |
The mean free path [ISO 80000-10:2009, item 10-73] of electrons. |
| |
| Reference type: |
PR |
| Reference: |
[ISO 80000-12:2009, item 12-16.a and item 12-16.2] |
| Supplemental references: |
|
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