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{{Expert-subject|Physics|date=February 2009}} |
{{Expert-subject|Physics|date=February 2009}} |
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In [[physics]], '''fluence''' is the [[flux]] (either particle or [[radiative flux]]) integrated over time. For particles, it is defined as the total number of particles that intersect a unit area in a specific time interval of interest, and has units of m<sup>–2</sup> (number of particles per meter squared). Fluence can also be used to describe the energy delivered per unit area, in which case it has units of J/m<sup>2</sup>. It is considered one of the fundamental units in [[dosimetry]]. |
In [[physics]], '''fluence''' is the [[flux]] (either particle or [[radiative flux]]) integrated over time. For particles, it is defined as the total number of particles that intersect a unit area in a specific time interval of interest, and has units of m<sup>–2</sup> (number of particles per meter squared). Fluence can also be used to describe the energy delivered per unit area, in which case it has units of J/m<sup>2</sup>. It is considered one of the fundamental units in [[dosimetry]]. |
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In light based medicine and dentistry, fluence, which may be more properly referred to as [[radiant exposure]], is a measurement of energy over area. The area is usually the spot size of the light device. |
In light based medicine and dentistry, fluence, which may be more properly referred to as [[radiant exposure]], is a measurement of energy over area. The area is usually the spot size of the light device. |
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Revision as of 16:24, 14 January 2014
This article needs attention from an expert in Physics. Please add a reason or a talk parameter to this template to explain the issue with the article.(February 2009) |
In physics, fluence is the flux (either particle or radiative flux) integrated over time. For particles, it is defined as the total number of particles that intersect a unit area in a specific time interval of interest, and has units of m–2 (number of particles per meter squared). Fluence can also be used to describe the energy delivered per unit area, in which case it has units of J/m2. It is considered one of the fundamental units in dosimetry.
Mocomnonjnxdjdjckcjvmcvnmmvm. VcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnjVcbsfhkmmknknknjknkjkninjnjnjbubunbubunjnjonjnjnjnjnjnjnj
In light based medicine and dentistry, fluence, which may be more properly referred to as radiant exposure, is a measurement of energy over area. The area is usually the spot size of the light device.
It has two equivalent definitions:
1. Suppose N particles pass through an area A. The particle fluence for the area A is defined as:
- .
In the limit of infinitesimal area, this is:
- .
2. Imagine an infinitesimal volume dV with particles passing through it. The particle fluence can be defined as
- ,
where is the sum of all the path lengths of the particles that traverse the volume. These definitions are equivalent as can be seen by multiplying the first definition by where dx is the typical path length of a particle in the volume. The numerator () then gives the total path length traced out by the dN particles in the volume () while the denominator () gives the volume dV.
References
- ICRU 33: Radiation Quantities and Units, April, 1980. (www.icru.org)
Quantity | Unit | Dimension | Notes | ||
---|---|---|---|---|---|
Name | Symbol[nb 1] | Name | Symbol | ||
Radiant energy | Qe[nb 2] | joule | J | M⋅L2⋅T−2 | Energy of electromagnetic radiation. |
Radiant energy density | we | joule per cubic metre | J/m3 | M⋅L−1⋅T−2 | Radiant energy per unit volume. |
Radiant flux | Φe[nb 2] | watt | W = J/s | M⋅L2⋅T−3 | Radiant energy emitted, reflected, transmitted or received, per unit time. This is sometimes also called "radiant power", and called luminosity in Astronomy. |
Spectral flux | Φe,ν[nb 3] | watt per hertz | W/Hz | M⋅L2⋅T −2 | Radiant flux per unit frequency or wavelength. The latter is commonly measured in W⋅nm−1. |
Φe,λ[nb 4] | watt per metre | W/m | M⋅L⋅T−3 | ||
Radiant intensity | Ie,Ω[nb 5] | watt per steradian | W/sr | M⋅L2⋅T−3 | Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity. |
Spectral intensity | Ie,Ω,ν[nb 3] | watt per steradian per hertz | W⋅sr−1⋅Hz−1 | M⋅L2⋅T−2 | Radiant intensity per unit frequency or wavelength. The latter is commonly measured in W⋅sr−1⋅nm−1. This is a directional quantity. |
Ie,Ω,λ[nb 4] | watt per steradian per metre | W⋅sr−1⋅m−1 | M⋅L⋅T−3 | ||
Radiance | Le,Ω[nb 5] | watt per steradian per square metre | W⋅sr−1⋅m−2 | M⋅T−3 | Radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. This is a directional quantity. This is sometimes also confusingly called "intensity". |
Spectral radiance Specific intensity |
Le,Ω,ν[nb 3] | watt per steradian per square metre per hertz | W⋅sr−1⋅m−2⋅Hz−1 | M⋅T−2 | Radiance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅sr−1⋅m−2⋅nm−1. This is a directional quantity. This is sometimes also confusingly called "spectral intensity". |
Le,Ω,λ[nb 4] | watt per steradian per square metre, per metre | W⋅sr−1⋅m−3 | M⋅L−1⋅T−3 | ||
Irradiance Flux density |
Ee[nb 2] | watt per square metre | W/m2 | M⋅T−3 | Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity". |
Spectral irradiance Spectral flux density |
Ee,ν[nb 3] | watt per square metre per hertz | W⋅m−2⋅Hz−1 | M⋅T−2 | Irradiance of a surface per unit frequency or wavelength. This is sometimes also confusingly called "spectral intensity". Non-SI units of spectral flux density include jansky (1 Jy = 10−26 W⋅m−2⋅Hz−1) and solar flux unit (1 sfu = 10−22 W⋅m−2⋅Hz−1 = 104 Jy). |
Ee,λ[nb 4] | watt per square metre, per metre | W/m3 | M⋅L−1⋅T−3 | ||
Radiosity | Je[nb 2] | watt per square metre | W/m2 | M⋅T−3 | Radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area. This is sometimes also confusingly called "intensity". |
Spectral radiosity | Je,ν[nb 3] | watt per square metre per hertz | W⋅m−2⋅Hz−1 | M⋅T−2 | Radiosity of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m−2⋅nm−1. This is sometimes also confusingly called "spectral intensity". |
Je,λ[nb 4] | watt per square metre, per metre | W/m3 | M⋅L−1⋅T−3 | ||
Radiant exitance | Me[nb 2] | watt per square metre | W/m2 | M⋅T−3 | Radiant flux emitted by a surface per unit area. This is the emitted component of radiosity. "Radiant emittance" is an old term for this quantity. This is sometimes also confusingly called "intensity". |
Spectral exitance | Me,ν[nb 3] | watt per square metre per hertz | W⋅m−2⋅Hz−1 | M⋅T−2 | Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m−2⋅nm−1. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity". |
Me,λ[nb 4] | watt per square metre, per metre | W/m3 | M⋅L−1⋅T−3 | ||
Radiant exposure | He | joule per square metre | J/m2 | M⋅T−2 | Radiant energy received by a surface per unit area, or equivalently irradiance of a surface integrated over time of irradiation. This is sometimes also called "radiant fluence". |
Spectral exposure | He,ν[nb 3] | joule per square metre per hertz | J⋅m−2⋅Hz−1 | M⋅T−1 | Radiant exposure of a surface per unit frequency or wavelength. The latter is commonly measured in J⋅m−2⋅nm−1. This is sometimes also called "spectral fluence". |
He,λ[nb 4] | joule per square metre, per metre | J/m3 | M⋅L−1⋅T−2 | ||
See also: |
- ^ Standards organizations recommend that radiometric quantities should be denoted with suffix "e" (for "energetic") to avoid confusion with photometric or photon quantities.
- ^ a b c d e Alternative symbols sometimes seen: W or E for radiant energy, P or F for radiant flux, I for irradiance, W for radiant exitance.
- ^ a b c d e f g Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek letter nu, not to be confused with a letter "v", indicating a photometric quantity.)
- ^ a b c d e f g Spectral quantities given per unit wavelength are denoted with suffix "λ".
- ^ a b Directional quantities are denoted with suffix "Ω".