In the previous article, we discussed “How to take care of your sunglasses?”. In this article, let’s talk about “What is the highest UV rating for sunglasses?”.
UV index and UV rating
The UV light in sunlight is a kind of light that is invisible, and the wavelength of UV light in the electromagnetic spectrum is -400nm. It is divided into A rays, B rays, and C rays (UVA, UVB, and UVC for short) with wavelengths ranging from 400-315nm, 315-280nm, and 280-190nm, respectively. The higher the UV index is, the more severe the damage to erythema caused by UV radiation is. Similarly, the higher the UV index is, the more serious the damage to the skin is in a short period. The UV index commonly begins at 0 and ends at (including more than ). According to these values, the meteorological bureau divides the forecast level of the UV index into five levels. When the UV index value is 0-2, the UV intensity is the lowest, the forecast level is 1; When the UV index value is 3-4, it is low, the forecast level is 2; When the UV index value is 5-6, it is high, the forecast level is 3; When the UV index value is 7-9, the intensity is very high, the forecast level is four; When the UV index value reaches or exceeds , the intensity is particularly high, the forecast level is five.
Confirmation of anti-UV function of sunglasses
Whether to confirm a pair of sunglasses can hold back ultraviolet rays is very simple. The first view is to find out if they have national criteria qb2457-1999 and gb8.3-2006. This is the unified grade in domestic sunglasses production. It blocks at least 95 percent of UVA and 99 percent of UVB. If it is in the domestic sales of professional sunglasses, the certificate can be seen on the two standards. The second one is to check if the UV value is more than 380, mostly VU380 or UV400. Professional sunglasses with UV protection feature the label of 0%UV or UV400, which effectively blocks the UV light with wavelengths up to 400nm.
Maximum UV protection rating for sunglasses
For sunglasses, the UV index, or UV filtering, should be between 280 and 400nm (i.e., nanometers). The 'UV index,' or how well the UV rays are filtered is an important criterion when buying sunglasses. Light with a wavelength between 286nm and 400nm is called UV light, and usually, a 0% UV index is impossible. Most sunglasses have a UV index between 96% and 98%. Sunglasses with anti-UV ability always have the following ways: a) label 'UV400': This means that the lens's UV cutoff wavelength is 400nm, that is, the * maximum of its spectral transmission at the wavelength (λ) below 400nm τ Max (λ) is not more than 2p; B) Labels 'UV' and 'UV protection': This means that the cutoff wavelength of the lens to UV is 380nm, that is, the * maximum of its spectral transmission at the wavelength (λ) below 380nm τ Max (λ) is not more than 2; C) Mark '0%UV absorption': This means that the lens has the function of 0% UV absorption, that is, its average transmission ratio in the UV coverage is not more than 0.5%.
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