What is best UV sunglasses The main function of the UV mirror is to absorb ultraviolet light with wavelengths up to 400 nanometers, without filtering other visible or invisible light.It filters UV rays because the lens contains lead, so UV lenses are heavier than other lenses of the same size and thickness. UV mirrors are also called ultraviolet filters, or Ultra Violet.Usually colorless and transparent, but some because of the anti-reflection film, at some angles will appear purple or purplish red.A lot of people buy UV lens to protect delicate lens coating film, actually this is just an accessory function of it.UV sunglasses.