As to 7→1→5→18 http://en.wikipedia.org/wiki/Ultraviolet 看到Glass似忽可以「挡」紫外线，所以就翻了一下网路上的资料， 然後发现 Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths while Silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm 所以，其实挡不挡还是要看材质。 UVA, UVB, UVC etc来说，照文章意思好像是UVA挡一部份，UVB, UVC挡掉（视材质）。 但因为UVA最弱（以hν=能量而言）所以是有挡一些的作用。 Eye High intensities of UVB light are hazardous to the eyes, and exposure can cause welder's flash (photokeratitis or arc eye) and may lead to cataracts, pterygium [9] [10], and pinguecula formation. Protective eyewear is beneficial to those who are working with or those who might be exposed to ultraviolet radiation, particularly short wave UV. Given that light may reach the eye from the sides, full coverage eye protection is usually warranted if there is an increased risk of exposure, as in high altitude mountaineering. Mountaineers are exposed to higher than ordinary levels of UV radiation, both because there is less atmospheric filtering and because of reflection from snow and ice. Ordinary, untreated eyeglasses give some protection. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrylic plastic used for lenses is less so. Some plastic lens materials, such as polycarbonate, inherently block most UV. There are protective treatments available for eyeglass lenses that need it which will give better protection. But even a treatment that completely blocks UV will not protect the eye from light that arrives around the lens. 不过即使可以挡，对周围的皮肤还是有伤害的。而且还是用塑胶的护目镜为宜。 --

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