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GCSE Physics · key term
The emission of visible light by a substance after it has absorbed radiation such as ultraviolet.
Used by Edexcel and OCR
Specification 5.22 · Paper 1
Revise: Uses of Visible Light and UltravioletUV can be absorbed by particular substances and produce effects such as fluorescence or damage to microorganisms. These different interactions make the two radiations useful in different ways.
Specification P6.1i · Paper 2 (Foundation), Paper 4 (Higher)
The emission of visible light by a substance after it has absorbed electromagnetic radiation, often ultraviolet radiation.
Do not say that ultraviolet itself is the visible glow. In fluorescence, ultraviolet is absorbed and visible light is then emitted.
In an explanation of fluorescence, state both stages: higher-frequency radiation is absorbed and lower-frequency visible light is emitted.
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Fluorescence demonstrates that absorbed and emitted radiation need not have the same frequency. Under a black light lamp, ultraviolet radiation is absorbed by fluorescent substances such as quinine in tonic water. Some of the absorbed energy is transferred within the substance, and visible blue light is then emitted.