![]() Armistead and Stanley Donald Stookey at the Corning Glass Works Inc. Photochromic lenses were developed by William H. These processes are reversible once the lens is removed from strong sources of UV rays the photochromic compounds return to their transparent state. ![]() In another sort of technology, organic photochromic molecules, when exposed to ultraviolet (UV) rays as in direct sunlight, undergo a chemical process that causes them to change shape and absorb a significant percentage of the visible light, i.e., they darken. They are transparent to visible light without significant ultraviolet component, which is normal for artificial lighting. In one sort of technology, molecules of silver chloride or another silver halide are embedded in photochromic lenses. ![]() A range of clear and dark transmittances is available. They darken significantly within about a minute of exposure to bright light and take somewhat longer to clear. They are principally used in glasses that are dark in bright sunlight, but clear, or more rarely, lightly tinted in low ambient light conditions. Glass lenses use visible light to darken. Photochromic lenses may be made of polycarbonate, or another plastic. In the absence of activating light, the lenses return to their clear state. Optical lenses that darken on exposure to certain wavelengths of lightĪ photochromic lens is an optical lens that darkens on exposure to light of sufficiently high frequency, most commonly ultraviolet (UV) radiation. ![]()
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