Sunglasses for UK women can protect your eyes from the glare of the light that is not comfortable. All this is due to the metal powder filter, which can be “selected” when the light comes in “. Can selectively absorb part of tainted glasses band composed of sun light, because it is a very fine powder with metal (iron, copper, nickel, etc.).
In fact, when the light shines on the lens of sunglasses with best sales, the so-called “interference” process based on light has been reduced. That is to say, when some wavelengths of light (here refers to the ultraviolet A, ultraviolet B, and sometimes infrared) through the lens, the inside of the lens that is toward the direction of the eye, they will offset each other. Overlapping is not an accidental phenomenon: a form of light wave with the wave trough close together, leading to offset each other.
The refractive index of the lens depends on the interference phenomenon (deviation degree that light from the air through different substances), also depends on the thickness of the lens of cheap sunglasses. Generally speaking, lens thickness change is not big, and lens refractive index is different according to the difference of chemical composition.