radiant intensity, $I$

Also contains definition of: intensity

Radiant power, $P$ , at all wavelengths per solid angle, $Ω$ . The radiant poweremitted in a given direction by a source or an element of the source in a small cone containing the given direction divided by the solid angle of the cone. SI unit is $W sr −1$ .

Notes:

Mathematical definition: $I = d P / d Ω$ . If the radiant power is constant over the solid angle considered, $I = P / Ω$ .
Equivalent to $I = ∫ λ I λ ⁢ d λ$ , where $I λ$ is the spectral radiant intensity at wavelength $λ$ .
It is not recommended to abbreviate this term to just intensity because it is confusing.

Source:

PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 410

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IUPAC > Gold Book > math/physics > quantities

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IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook.

Last update: 2014-02-24; version: 2.3.3.

DOI of this term: https://doi.org/10.1351/goldbook.R05045.

Original PDF version: http://www.iupac.org/goldbook/R05045.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.

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