Fluorescence
emission of light by a substance that has absorbed light
Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colored visible light. The color of the light emitted depends on the chemical composition of the substance. Fluorescent materials generally cease to glow nearly immediately when the radiation source stops. This distinguishes them from the other type of light emission, phosphorescence. Phosphorescent materials continue to emit light for some time after the radiation stops.
This difference in duration is a result of quantum spin effects.
Fluorescence occurs when a photon from incoming radiation is absorbed by a molecule, exciting it to a higher energy level, followed by the emission of light as the molecule returns to a lower energy state. The emitted light may have a longer wavelength and, therefore, a lower photon energy than the absorbed radiation. For example, the absorbed radiation could be in the ultraviolet region of the electromagnetic spectrum (invisible to the human eye), while the emitted light is in the visible region.
Begin with the source’s own compact description: “Fluorescence” is emission of light by a substance that has absorbed light. The dossier treats that line as a proposition to test through Fluorescence, emission and light, not as a finished interpretation.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 2, 2026. The linked authority identifier is Q191807. The Library of Congress control number is sh85049407. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Fluorescence” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.