Title: radiant exitance
Long Title: IUPAC Gold Book - radiant exitance
DOI: 10.1351/goldbook.R05041
Status: current
Index: quantity

Definition
Radiant power, \(P\), emitted at all wavelengths by an element of surface containing the source point under consideration divided by the area of the source. SI unit is \(\rm{W m}^{-2}\).

Notes
1) Mathematical definition: \(M = \rm{d}P/\rm{d}S\). If the radiant power \(P\) is constant over the surface area considered, \(M = P/S\).
2) Equivalent to the integration of the radiant power leaving a source over the solid angle and over the whole wavelength range. Mathematical definition: \(M = \int_{\lambda}M_{\lambda}\, \rm{d}\lambda\), where \(M_{\lambda}\) is the spectral radiant exitance at wavelength \(\lambda\).
3) Same as spherical radiant exitance. Formerly called radiant emittance.

Related Terms
- Radiant power: https://goldbook.iupac.org//terms/view/R05046
- angle: https://goldbook.iupac.org//terms/view/A00346
- spectral radiant exitance: https://goldbook.iupac.org//terms/view/S05825
- wavelength: https://goldbook.iupac.org//terms/view/W06659

Source
- PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 409 (https://doi.org/10.1351/pac200779030293)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/R05041/html
- json: https://goldbook.iupac.org/terms/view/R05041/json
- xml: https://goldbook.iupac.org/terms/view/R05041/xml

Citation: Citation: 'radiant exitance' 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.R05041
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Accessed: 2026-04-19T02:15:26+00:00