Check out your eyes for reading glasses
Photochromic glasses automatically change from clear to dark in the presence of sunlight. It looks pretty good but apart from good things it has few practical problems as well. Anyways, one should not have doubt upon its demand and popularity which has induced prominent online eyeglass seller 'Cheapglassesdirect.com' to sell and regularly update photochromic segment of eye glasses in its spectacles store.
From literary point of view, it means ‘transition or sun-sensor’. Photochromic lenses become darker if it exposes towards ultra violet rays. One should have very clear idea that photochromic lenses does not be dark due to brightness hence the fact is being repeated here that photochromic lenses become dark only in the presence of ultraviolet rays. Such lenses use to be inversely temperature sensitive as well. In simpler form, one can interpret it as photochromic lenses becomes darker in hot weather on the other hand in cold weather it looses its darkness.
Well! It may be bad to hear especially for car users but the fact is, ‘photochromic glasses do not darken even inside the car’ because very less amount of ultra violet rays enters into the car. On the contrary, even on cloudy days, it may be darken outside because of the presence of ample amount of ultra violet rays.
Eye glasses freak or in more humble words, we should say ‘hardcore eyeglass users’ do not hesitate to carry up to 2-3 spectacles. The categories might be like, one eye glass with normal clear lens for cloudy day, second-one might be photochromic and the third-one may be a dark bifocal sunglass. Well! All these are now not so expensive as well because Cheapglassesdirect.com is offering wide ranges of cheap eyeglasses, and discount eyeglasses.
Suppose, the day is turning into night and your photochromic eyeglasses’ darkness is still too dark. You are hardly getting crystal clear vision. Well! No need to worry, just have some patience, wait for 5-10 minutes and soon darkness will disappear and you could get clearer vision in night. You can get sooner as well just by dipping into warm water. Now a very interesting question comes into our mind, “why darkening effect of photochromic work better in cold, though chemistry suggest that chemical reaction fastens in warmness?” The answer is, “it is not chemical reaction, it is electrochemical effect”.