Radiometry
Encyclopedia : R : RA : RAD : Radiometry
In telecommunications and physics, radiometry is the field that studies the measurement of electromagnetic radiation, including visible light. Note that light is also measured using the techniques of photometry, which deal with brightness as perceived by the human eye, rather than absolute power.
| 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 emittance / Radiant exitance | M | watt per square metre | W·m−2 | power emitted from a surface. Sometimes confusingly called "intensity". |
| 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 |
External links
- [Radiometry and photometry FAQ] Professor Jim Palmer's Radiometry FAQ page (University of Arizona).
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