Title: radiant exposure
Long Title: IUPAC Gold Book - radiant exposure
DOI: 10.1351/goldbook.R05042
Status: current
Index: quantity

Definition
Radiant energy, \(Q\), incident from all upward directions on a small sphere divided by the cross-sectional area of that sphere. SI unit is \(\pu{J m-2}\).

Notes
1) Equivalent definition: Irradiance, \(E\) integrated over the time of irradiation.
2) Mathematical definition: \(H = \rm{d}Q/\rm{d}S = \int _{t} E\, \rm{d}t\). If \(Q\) is constant over the area, \(H = Q/S\). If \(E\) is constant over the time interval, \(H = E\, t\).
3) This term refers to a beam not scattered or reflected by the target or its surroundings. For a beam incident from all directions fluence (\(H_{\rm{o}}\), \(F_{\rm{o}}\)) is an equivalent term.

Related Terms
- Radiant energy: https://goldbook.iupac.org/terms/view/R05039
- irradiation: https://goldbook.iupac.org/terms/view/I03255

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/R05042/html
- json: https://goldbook.iupac.org/terms/view/R05042/json
- xml: https://goldbook.iupac.org/terms/view/R05042/xml

Citation: Citation: 'radiant exposure' 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.R05042
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Accessed: 2026-07-29T11:58:47+00:00