l*******s
发帖数: 7316 | 1 为什么外出变暗，回到室内变亮？
变暗快还是变亮快？为什么？ | c******n
发帖数: 16666 | | H********g
发帖数: 43926 | 3 现代太阳镜用见UV变色的有机染料naphthopyrans
http://www.explainthatstuff.com/photochromiclenses.html
Modern photochromic lenses tend to be plastic and instead of silver
chemicals they contain organic (carbon-based) molecules called naphthopyrans
that react to light in a slightly different way: they subtly change their
molecular structure when ultraviolet light strikes them. In this altered
form, they soak up more ordinary light as it tries to pass by (technically,
we say they have a different absorption spectrum), which is what makes the
lenses darken. | H********g
发帖数: 43926 | 4 15分钟内变色
About half the darkening happens within the first minute and they're cutting
out about 80% of sunlight within 15 minutes.
缺点是恢复透明状态比较慢
Unfortunately, it takes a little bit longer for photochromic lenses to clear
than it does for them to darken in the first place. Generally, they let
through about 60% of light again after you've been back indoors for five
minutes. However, it can take up to an hour for them to clear completely.
而且车里不好用，因为车玻璃挡了UV
A related problem is that photochromic lenses don't always work effectively
in cars, because ordinary glass windscreens naturally screen out most of the
ultraviolet light. That means drivers really need a second pair of tinted
or polarized sunglasses just for driving in. | l*******s
发帖数: 7316 | 5 确实恢复透明状态比较慢。车里还好，虽然紫外线被挡了一些，但变色太阳镜还是会变
得很暗。
cutting
clear
effectively
【在 H********g 的大作中提到】
: 15分钟内变色
: About half the darkening happens within the first minute and they're cutting
: out about 80% of sunlight within 15 minutes.
: 缺点是恢复透明状态比较慢
: Unfortunately, it takes a little bit longer for photochromic lenses to clear
: than it does for them to darken in the first place. Generally, they let
: through about 60% of light again after you've been back indoors for five
: minutes. However, it can take up to an hour for them to clear completely.
: 而且车里不好用，因为车玻璃挡了UV
: A related problem is that photochromic lenses don't always work effectively
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