08242 IUPAC Gold Book - electromagnetic radiation 10.1351/goldbook.08242 08242 current initialism: EM 1 Flow of energy through space propagated as synchronized sinusoidal waves of the electric field, \(\boldsymbol{E}\), and the magnetic field \(\boldsymbol{H}\). Electromagnetic radiation is characterized by frequency \(\nu\), wavelength \(\lambda\), and speed \(c\), where \(\nu\lambda = c\). The wavelength and velocity change when radiation enters a medium. In its interaction with atoms and molecules, radiation behaves like particles, called photons, with zero mass, energy \(h\nu\), and momentum \(h/\lambda\), where \(h\) is the Planck constant \(h = \pu{6.62607015E-34 J s}\). wavelength https://goldbook.iupac.org//terms/view/08299 PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 657 (https://doi.org/10.1515/pac-2019-0203) https://goldbook.iupac.org/terms/view/08242/html https://goldbook.iupac.org/terms/view/08242/json https://goldbook.iupac.org/terms/view/08242/plain Citation: 'electromagnetic radiation' 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.08242 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-05-30T13:16:30+00:00