How do photochromatic lenses work?

[aommaster]

A very confusing topic to define in a category. How do photochromatic lenses work? You know those glasses that are transpaerent and when exposed to sunlight, they darken? How do they work, from the name, I can guess that it has something to do with light, other thatn that, i have absolutely no idea! How do they work? What chemical do they have in them that makes them behave like this?

[wolfson]

http://www.corning.com/ophthalmic/discovery_center/

 

Hope that helps

[agaubr]

The normal method is related to the chemistry of silver which when exposed to the ligth darkens and then reverst back in the dark.

[aommaster]

Thanx alot guys!