Photochromic lens
optical lenses that darken on exposure to certain wavelengths of light
A photochromic lens is an optical lens that darkens on exposure to light of sufficiently high frequency, most commonly ultraviolet (UV) radiation. In the absence of activating light, the lenses return to their clear state. Photochromic lenses may be made of polycarbonate, or another plastic. Glass lenses use visible light to darken. They are principally used in glasses that are dark in bright sunlight, but clear, or more rarely, lightly tinted in low ambient light conditions. They darken significantly within about a minute of exposure to bright light and take somewhat longer to clear. A range of clear and dark transmittances is available. Two kinds of photochromic lenses were popularized, the first being glass containing silver halides. These silver-based lenses became largely obsolete with the introduction of photochromic organic compounds. The other type are plastic, usually polycarbonate combined with photochromic organic compounds.
Begin with the source’s own compact description: “Photochromic lens” is optical lenses that darken on exposure to certain wavelengths of light. The dossier treats that line as a proposition to test through Photochromic, lens and optical, not as a finished interpretation.
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This entry incorporates text from “Photochromic lens” 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.