Title: radiation constants
Long Title: IUPAC Gold Book - radiation constants
DOI: 10.1351/goldbook.R05051
Status: current
Index: constant

Definition
Fundamental physical constants characterizing black body radiation. The first radiation constant is \(c_{1} = 2\ \pi \ h\ c_{0}^{2}=3.741\,7749(22)\times 10^{-16}\ \rm{W m}^{2}\), the second is \(c_{2} = \frac{h\ c_{0}}{k}=1.438\,769(12)\times 10^{-2}\ \rm{m K}\), where \(h\) is the Planck constant \(c_{0}\) the speed of light and \(k\) the Boltzmann constant.

Related Terms
- Boltzmann constant: https://goldbook.iupac.org//terms/view/B00695
- Planck constant: https://goldbook.iupac.org//terms/view/P04685

Source
- CODATA Bull. 1986, 63, 1 (https://doi.org/10.6028/jres.092.010)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/R05051/html
- json: https://goldbook.iupac.org/terms/view/R05051/json
- xml: https://goldbook.iupac.org/terms/view/R05051/xml

Citation: Citation: 'radiation constants' 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.R05051
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Accessed: 2026-04-20T12:46:18+00:00