Principle of sunglasses

Sunglasses can block glare of uncomfortable, at the same time can protect your eyes from uv rays. All of this is due to metal powder filters, they can when light hits on the 'choice'. Of colored glasses can selectively absorb the sun's rays of a part of the band, because it is through the thin metal powder ( Iron, copper, nickel, etc. ) 。 In fact, when the light on the lenses, based on the so-called 'destructive interference' process, the light is reduced. In other words, when certain wavelengths of light ( Here refers to uva, uvb rays, and sometimes infrared) Through the lens, the lens inside the eye direction, they will cancel each other out. Formation of overlapping of waves is not an accidental phenomenon: a wave crest with the wave trough of near together, leads to cancel each other out. Destructive interference phenomenon depends on the lens refraction coefficient ( The different material from the air through the light when the degree of deviation) , also depends on the thickness of the lens. Little change in general, the thickness of the lens, the lens refractive index was based on the differences of chemical composition and different. Polarized glasses, provides another mechanism of protecting our eyes. The asphalt reflected light is a special polarized light. The reflected light and the light from the sun directly or any artificial light source the light is different from the problem lies in the order. Polarized light is made up of all in one direction vibration wave form, and the light of the general is by not directional vibration wave into the open. It's like a group of people walk around with a group of no order with neat pace of marching soldiers, to the stark. Generally speaking, the reflected light is the light of an orderly. Polarized lens was especially effective in blocking the light, because its filtrability at work. This kind of lens only let in a certain direction vibration by polarized wave, like will light 'comb'. To the problem of road reflectors using polarized glasses can reduce light transmission, because it does not transfer parallel shock waves through the road. In fact, the filter layer long molecules are oriented horizontally, can absorb horizontally polarized light. In this way, most of the reflected light is eliminated, and the whole lighting degree did not reduce the surrounding environment. After color glasses lens can after the sun's rays to darken. When lighting weakens, it became bright again. To be able to, because of the silver halide crystals at work. Under normal circumstances, it can keep the lens transparency. Not in the sunlight, silver was separated from crystal, silver in YouLiZhuang inside the lens form small drupelets. These small silver aggregation of jagged irregular mass, they cannot be transmitted light, and can only absorb light, the result has lenses darkened. In the light from the darkness of the crystal, and heavy form, lens then return to the bright state.