The sun glasses the deeper the color uv protection is better?

Sunglasses in our daily life is common and is practical, but some common sense about the sunglasses is not knows every wear sunglasses, such as what kind of sun glasses is good, the lens should choose what kind of color to uv protection, and so on. Some people think that the color of the sunglasses the deeper the uv protection function, the better, so what is this? A lot of people think the depth of the lens color is proportional to the uv protection performance, but in fact no relationship between the two, because the lens color depth refers to the visible light transmittance, you can judge with the naked eye, and the ultraviolet ray is visible to the naked eye cannot be observed, the lens uv protection performance can only through specific focal meter and spectrum analyzer can be detected, such as the minus reflection film plating PC lens, light transmittance as high as 99%, uv protection performance is reached almost 100%. If the lens does not uv lens color the deeper the greater the damage to the eyes, because in the sun wearing dark sunglasses pupil will loose big because of light reflex, cannot prevent ultraviolet ray again into the lens itself, so ultraviolet ray did not decrease per unit area, and to accept the light of the pupil area is increased, so get more into the eyes of the ultraviolet ray, is wearing dark sunglasses uv than not wearing sunglasses the damage to the eyes.
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