The quality 1.56 Finish Photochromic Progressive Brown lens contains silver halide (silver chloride, silver bromide) crystallites, and when irradiated by activating light such as ultraviolet light or short-wave visible light, halide ions emit electrons, which are captured by silver ions. The following reactions occur in the quality 1.56 Finish Photochromic Progressive Brown lens: the colorless silver halide is decomposed into opaque silver atoms and transparent halogen atoms, and the silver atoms absorb light to reduce the light transmittance of the lens.Since the halogens in the quality 1.56 Finish Photochromic Progressive Brown lens do not escape, a reversible reaction occurs. After the activating light is removed, the silver and halogen recombine, returning the lens to its original clear, colorless, or light-tinted state. Glass containing silver bromide (or silver chloride) and trace amounts of copper oxide in quality 1.56 Finish Photochromic Progressive Brown lens is a color-changing glass. When exposed to sunlight or ultraviolet rays, the silver bromide in it decomposes, producing silver atoms.Silver atoms can attract visible light. When the silver atoms gather to a certain amount, most of the light incident on the glass of the quality 1.56 Finish Photochromic Progressive Brown lens is absorbed, and the original colorless and transparent glass will become gray-black at this time. When the discolored glass is placed in a dark place, under the catalysis of copper oxide, silver atoms and bromine atoms will combine to form silver bromide, because silver ions do not absorb visible light, so the glass will again Become colorless, and transparent. This is the basic principle behind the quality 1.56 Finish Photochromic Progressive Brown lens.