Title: radiant power
Long Title: IUPAC Gold Book - radiant power
DOI: 10.1351/goldbook.R05046
Status: current
Index: quantity

Definition
Power emitted, transferred or received as radiation. SI unit is \(\pu{J s-1} = \pu{W}\).

Notes
1) Mathematical definition: \(P = \rm{d}Q/\rm{d}t\). If the radiant energy \(Q\) is constant over the time interval, \(P = Q/t\).
2) In radiometry, flux (\(\varPhi\)) is used with the same units as \(P\). The symbol \(\varPhi\) is reserved for quantum yield in photochemistry. Therefore, the use of flux (\(\varPhi\)) is not recommended.

Related Terms
- Power: https://goldbook.iupac.org/terms/view/P04792
- photochemistry: https://goldbook.iupac.org/terms/view/P04588
- quantum yield: https://goldbook.iupac.org/terms/view/Q04991
- radiant energy: https://goldbook.iupac.org/terms/view/R05039
- radiometry: https://goldbook.iupac.org/terms/view/R05115

Source
- PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 410 (https://doi.org/10.1351/pac200779030293)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/R05046/html
- json: https://goldbook.iupac.org/terms/view/R05046/json
- xml: https://goldbook.iupac.org/terms/view/R05046/xml

Citation: Citation: 'radiant power' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.R05046
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Accessed: 2026-05-10T16:47:59+00:00