Radiant flux
From Wikipedia, the free encyclopedia
 |
This article needs additional citations for verification. (December 2009) |
In radiometry, radiant flux or radiant power is the measure of the total power of electromagnetic radiation (including infrared, ultraviolet, and visible light). The power may be the total emitted from a source, or the total landing on a particular surface.
Units [edit]
The SI unit of radiant flux is the watt (W), which has dimensions of energy/time or, in SI units joules/second.
SI radiometry units
| Quantity | Unit | Dimension | Notes | |||||
|---|---|---|---|---|---|---|---|---|
| Name | Symbol[nb 1] | Name | Symbol | Symbol | ||||
| Radiant energy | Qe[nb 2] | joule | J | M⋅L2⋅T−2 | energy | |||
| Radiant flux | Φe[nb 2] | watt | W | M⋅L2⋅T−3 | radiant energy per unit time, also called radiant power. | |||
| Spectral power | Φeλ[nb 2][nb 3] | watt per metre | W⋅m−1 | M⋅L⋅T−3 | radiant power per wavelength. | |||
| Radiant intensity | Ie | watt per steradian | W⋅sr−1 | M⋅L2⋅T−3 | power per unit solid angle. | |||
| Spectral intensity | Ieλ[nb 3] | watt per steradian per metre | W⋅sr−1⋅m−1 | M⋅L⋅T−3 | radiant intensity per wavelength. | |||
| Radiance | Le | watt per steradian per square metre | W⋅sr−1⋅m−2 | M⋅T−3 | power per unit solid angle per unit projected source area. confusingly called "intensity" in some other fields of study. |
|||
| Spectral radiance | Leλ[nb 3] or Leν[nb 4] |
watt per steradian per metre3 or watt per steradian per square |
W⋅sr−1⋅m−3 or W⋅sr−1⋅m−2⋅Hz−1 |
M⋅L−1⋅T−3 or M⋅T−2 |
commonly measured in W⋅sr−1⋅m−2⋅nm−1 with surface area and either wavelength or frequency. |
|||
| Irradiance | Ee[nb 2] | watt per square metre | W⋅m−2 | M⋅T−3 | power incident on a surface, also called radiant flux density. sometimes confusingly called "intensity" as well. |
|||
| Spectral irradiance | Eeλ[nb 3] or Eeν[nb 4] |
watt per metre3 or watt per square metre per hertz |
W⋅m−3 or W⋅m−2⋅Hz−1 |
M⋅L−1⋅T−3 or M⋅T−2 |
commonly measured in W⋅m−2⋅nm−1 or 10−22W⋅m−2⋅Hz−1, known as solar flux unit.[nb 5] |
|||
| Radiant exitance / Radiant emittance |
Me[nb 2] | watt per square metre | W⋅m−2 | M⋅T−3 | power emitted from a surface. | |||
| Spectral radiant exitance / Spectral radiant emittance |
Meλ[nb 3] or Meν[nb 4] |
watt per metre3 or watt per square |
W⋅m−3 or W⋅m−2⋅Hz−1 |
M⋅L−1⋅T−3 or M⋅T−2 |
power emitted from a surface per wavelength or frequency. |
|||
| Radiosity | Je or Jeλ[nb 3] | watt per square metre | W⋅m−2 | M⋅T−3 | emitted plus reflected power leaving a surface. | |||
| Radiant exposure | He | joule per square metre | J⋅m−2 | M⋅T−2 | ||||
| Radiant energy density | ωe | joule per metre3 | J⋅m−3 | M⋅L−1⋅T−2 | ||||
| See also: SI · Radiometry · Photometry | ||||||||
- ^ Standards organizations recommend that radiometric quantities should be denoted with a 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 emittance.
- ^ a b c d e f Spectral quantities given per unit wavelength are denoted with suffix "λ" (Greek) to indicate a spectral concentration. Spectral functions of wavelength are indicated by "(λ)" in parentheses instead, for example in spectral transmittance, reflectance and responsivity.
- ^ a b c Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek)—not to be confused with the suffix "v" (for "visual") indicating a photometric quantity.
- ^ NOAA / Space Weather Prediction Center includes a definition of the solar flux unit (SFU).
See also [edit]
References [edit]
Boyd, Robert (1983). Radiometry and the Detection of Optical Radiation (Pure & Applied Optics Series). Wiley-Interscience. ISBN 978-0-471-86188-1.
 |
This optics-related article is a stub. You can help Wikipedia by expanding it. |
