Radiance
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Radiation intensity or radiation intensity , also called radiation intensity (but the term is also used in a different meaning - see intensity (physics) ), is a term from radiometry . The radiant intensity is the portion of the radiant power that is emitted by a radiation source (e.g. light source ) in a given spatial direction into the solid angle element of any small size :
The power is measured in watts (W), the solid angle in steradians (sr); the SI unit of the radiation intensity is therefore W / sr.
If the energy is radiated isotropically , i.e. within the entire solid angle of equally in each direction, the radiation intensity in each direction is:
- .
Photometric equivalent
The corresponding quantity in photometry is the light intensity . It results from the radiant intensity by them with the photometric radiation equivalent , which includes the sensitivity curve of the human eye, weighted .
Relationship with other radiometric quantities
radiometric quantity | Symbol a) | SI unit | description | photometric equivalent b) | symbol | SI unit |
Radiant flux radiant power, radiant flux, radiant power |
W ( watt ) |
Radiant energy through time |
Luminous flux luminous flux, luminous power |
lm ( lumens ) |
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Radiant intensity irradiance, radiant intensity |
W / sr | Radiation flux through solid angles |
Luminous intensity luminous intensity |
cd = lm / sr ( candela ) |
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Irradiance irradiance |
W / m 2 | Radiation flux through the receiver surface |
Illuminance illuminance |
lx = lm / m 2 ( lux ) |
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Specific radiation emission current density, radiant exitance |
W / m 2 | Radiation flux through the transmitter surface |
Specific light emission luminous exitance |
lm / m 2 | ||
Radiance radiance, radiance, radiance |
W / m 2 sr | Radiant intensity through effective transmitter area |
Luminance luminance |
cd / m 2 | ||
Radiant energy amount of radiation, radiant energy |
J ( joules ) |
by radiation transmitted energy |
Amount of light luminous energy, quantity of light |
lm · s | ||
Irradiation irradiation, radiant exposure |
J / m 2 | Radiant energy through the receiver surface |
Exposure luminous exposure |
lx s | ||
Radiation yield radiant efficiency |
1 | Radiation flux through absorbed (mostly electrical) power |
Luminous efficiency (overall) luminous efficacy |
lm / W |
Individual evidence
- ↑ Ludwig Bergmann , Clemens Schaefer : Optics: Wave and particle optics . In: Bergmann-Schaefer textbook on experimental physics . tape 3 . Walter de Gruyter, 2004, ISBN 3-11-017081-7 , p. 637 ( limited preview in Google Book search).
- ↑ electropedia , International Electrotechnical Dictionary (IEV) of the International Electrotechnical Commission : Entries 731-01-23 (area "fiber optic communication") and 845-01-30 (area lighting) have the translation: radiant intensity = "radiation intensity"
- ↑ Robert Wichard Pohl : Introduction to Optics . 8th edition. Springer, Heidelberg 1948, ISBN 978-3-662-01855-2 , p. 321 ff . (Online: [1] )
- ↑ electropedia , International Electrotechnical Dictionary (IEV) of the International Electrotechnical Commission : Entry 705-02-04 (section "Communication by radio waves") has the translation radiation intensity = "Radiation intensity (in a given direction)"; the German edition of the dictionary , published by the German Commission for Electrical, Electronic and Information Technologies , adds the footnote: "In lighting technology, preferably referred to as radiation intensity".