Sunglasses can block unpleasant glare and protect your eyes from the eye
Damaged by ultraviolet rays. All of this is due to the metal powder filter, which "selects" the light as it enters. Colored glasses selectively absorb some of the wavelength bands that make up the sun's rays because they rely on very fine metal powders (iron, copper, nickel, etc.). In fact, when light hits the lens, the light is diminished based on the so-called "destructive interference" process. That is to say, when light of certain wavelengths (herein referred to as ultraviolet light a, ultraviolet light b, and sometimes infrared light) passes through the lens, they cancel each other in the direction of the inner side of the lens, that is, toward the eye. The mutual overlap of the formation of light waves is not an accidental phenomenon: the peaks of one wave are combined with the waves of the waves that are close to them, resulting in mutual cancellation. The destructive interference phenomenon depends on the refractive index of the lens (ie, the extent to which light deviates from the air through different materials) and also depends on the thickness of the lens. In general, the thickness of the lens does not change much, and the refractive index of the lens varies depending on the chemical composition.