Sunglasses Effect

Sunglasses can block uncomfortable strong light and protect the eyes from UV damage. All of this is attributed to the metal powder filtration device, which can "select" it when light enters. Colored glasses can selectively absorb some of the wavelengths that make up sunlight because they use very fine metal powders (such as iron, copper, nickel, etc.). In fact, when light shines on the lens, it is subtracted based on the so-called "destructive interference" process. That is to say, when certain wavelengths of light (referring to ultraviolet a, ultraviolet b, and sometimes infrared) pass through the lens, they cancel out each other on the inside of the lens, facing the eye. The overlapping of light waves is not an accidental phenomenon: the peaks of a wave merge with the valleys of nearby waves, resulting in mutual cancellation. The phenomenon of destructive interference depends on the refractive index of the lens (i.e. the degree to which light deviates when passing through different substances from the air), as well as the thickness of the lens. Generally speaking, the thickness of the lens does not change much, while the refractive index of the lens varies depending on the chemical composition, and sunglasses cannot directly contact direct sunlight.