The damage of ultraviolet rays to human body is cumulative, that is to say, the longer exposure time to sunlight, the greater the damage of ultraviolet rays. Choose sunglasses, do not think that the darker the lens, the stronger the anti ultraviolet effect. On the contrary, the darker the color is, the bigger the pupil will become. If it is not safe to use anti ultraviolet lenses, the more ultraviolet rays the eyes will be exposed to, and the more serious the damage will be.
Therefore, it is best to confirm that the lens can effectively block more than 99% of ultraviolet (including ultraviolet A and ultraviolet B), and at the same time, it should have polarizing characteristics, so as to eliminate glare (glare refers to the strong light reflected from some angles to the eyes, which will make people temporarily unable to see clearly). Polarizing glasses have the theory of polarizing angle.
Principle of Polarized Sunglasses
Natural light (nonpolar light) is actually composed of electromagnetic waves that vibrate in a specific direction, and the reflected or scattered light usually prefers a specific direction, which is why polarized sunglasses can filter out the sunlight reflected from the roof or pool; after the natural light is filtered by the polarized lens, it can only let the light in one direction pass through, that is to say Polarizing lens can polarize the light first, and then allow only one direction of light to pass through (visible light).
Polarizing sunglasses use this feature to block harmful light, because the sunlight will produce harmful glare due to natural reflection or refraction when it touches any object. Polarizing sunglasses can completely absorb these strong light that will cause glare and eye damage.
Functions of Polarized Sunglasses
In life, too many light sources will produce harmful light, especially sunlight; the light emitted from sunlight includes visible light, infrared, ultraviolet and so on. Among them, ultraviolet rays cause serious damage to human skin, eyes, etc.; in the light released by sunlight, IR (infra red) is more than 750mm, visible light lay (310 ~ 780nm); ultraviolet rays are divided into UVA, UVB, UVC (310nm) and blue light ）Among them, UVA, UVB and UVC are harmful light. If exposed to the sun for a long time, it will cause damage to the body. UVB has a serious impact on the eyesight. Tanning ray is the light that burns the black skin. Most of the corners of the eyes will absorb this kind of UVB light, so we must block this kind of light source. Polarized sunglasses have the function of polarizing the light, so they can block all the harmful light without affecting the transmission of the visible light, and can really achieve the function of protecting the eyes.
Application of Polarized Sunglasses
Polarizing sunglasses can be used in the following fields because they can block harmful light 100%
Medical treatment: Patients with eye surgery need all-round protection, and polarized sunglasses are the best choice.
Outdoor activities: such as skiing, fishing, water activities, etc., all need sunglasses that can completely block harmful light to avoid eye injury or fatigue.
Comparison between general sunglasses and polarized sunglasses:
Ordinary Sunglasses only use the function of reducing light, because ordinary lenses can't filter light, so they can only reduce the intensity of glare, ultraviolet light, etc., and can't completely block these harmful light, so their function is only to reduce eye damage, but the biggest advantage of ordinary sunglasses is good popularity. Polarizing lenses can completely block glare caused by scattering, refraction, reflection and other factors because of their polarizing properties. At the same time, it can also completely block the harmful ultraviolet light to the human eyes, so that when people move for a long time under strong light, the eyes are not easy to get tired, so as to achieve the function of real protection, and make the things they see more clear and three-dimensional.