Molecules of silver chloride or another silver halide are embedded in photochromatic lenses. They are transparent to visible light without a lot of ultraviolet light, which is normal for artificial lighting. In another kind, organic photochromic molecules, when exposed to uv rays like in direct sunlight, go through a chemical process that makes them to change shape and absorb a large amount of the visible light (making them dark)
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It’s mostly used in eyeglasses
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It’s mostly used in eyeglasses