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Radiant intensity
In radiometry, radiant intensity is a measure of the intensity of electromagnetic radiation. It is defined as power per unit solid angle. The SI unit of radiant intensity is watts per steradian (W·sr-1). It is distinct from intensity defined by irradiance or radiant exitance which measure radiation directed at or emitted from a given surface area.
See also
- Candela
- Luminous intensity
- Intensity
[edit]
SI radiometry units
| Quantity |
Symbol |
SI unit |
Abbr. |
Notes |
| Radiant energy |
Q |
joule |
J |
energy |
| Radiant flux |
Φ |
watt |
W |
radiant energy per unit time, also called radiant power |
| Radiant intensity |
I |
watt per steradian |
W·sr−1 |
power per unit solid angle |
| Radiance |
L |
watt per steradian per square metre |
W·sr−1·m−2 |
power per unit solid angle per unit projected source area.
Sometimes confusingly called "intensity".
|
| Irradiance |
E |
watt per square metre |
W·m−2 |
power incident on a surface.
Sometimes confusingly called "intensity".
|
| Radiant exitance / Radiant emittance |
M |
watt per square metre |
W·m−2 |
power emitted from a surface. |
| Radiosity |
J or Jλ |
watt per square metre |
W·m−2 |
emitted plus reflected power leaving a surface |
| Spectral radiance |
Lλ
or
Lν |
watt per steradian per metre3 or
watt per steradian per square metre per hertz
|
W·sr−1·m−3
or
W·sr−1·m−2·Hz−1
|
commonly measured in W·sr−1·m−2·nm−1 |
| Spectral irradiance |
Eλ
or
Eν |
watt per metre3 or
watt per square metre per hertz |
W·m−3
or
W·m−2·Hz−1 |
commonly measured in W·m−2·nm−1 |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Radiant_intensity". A list of authors is available in Wikipedia.
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