The difference between cheap sunglasses and expensive sunglasses

The biggest difference between cheap and expensive sunglasses is the different lens materials. Cheap sunglasses lenses are ordinary plastic lenses with poor clarity and shape, while expensive sunglasses are crystal lenses with good clarity and shape.

According to the national standard, the outer packaging of regular anti-ultraviolet sunglasses must be marked with anti-ultraviolet grades, including UVA (filtering wavelength is 320-420 nm), UVB (filtering wavelength is 275-320 nm) and UV400 (filtering wavelength is below 400 nm).

All three have anti-ultraviolet function. Generally, the UV index of sunglasses is between 96% and 98%. Generally speaking, a UV index of 100% is impossible.

Sunglasses are the same size as frames and are designed and produced according to standard specifications. The size parameters of sunglasses are marked on temples, bridge of nose or signboards for reference. For example: 53- 16- 130, which means that the frame size is 53mm, the nose bridge size is 16mm and the temple size is 130mm.

The principle of sunglasses

Sunglasses can resist uncomfortable strong light and protect eyes from ultraviolet rays. All this is due to the metal powder filter, which can "select" the light when it enters. Colored glasses can selectively absorb some bands that make up the sun's rays because they use very fine metal powders (iron, copper, nickel, etc.). ).

In fact, when light strikes the lens, it is reduced based on the so-called "destructive interference" process. That is to say, when some wavelengths of light (here refers to ultraviolet A, ultraviolet B, and sometimes infrared rays) pass through the lens, they will cancel each other inside the lens, that is, in the direction towards the eyes.