How do Photochromic lenses work?

[Thalita Luna]

Photochromic lenses are common in glasses, they stay transparent indoor, but get darken when exposed to sunlight. How does it work ?

 

[berkeman]

Welcome to PF.

Google is your friend; following links are from searches on photochromic lens and photochromic molecule:

https://www.transitions.com/en-us/why-transitions/the-technology/photochromic-tech/

https://en.wikipedia.org/wiki/Photochromism