Photochromic glasses

Question 1

What happens to borosilicate glass when it’s exposed to UV radiation?

Answer 1

~ AgI + CuI –> Ag + CuI2

~ the Ag regions grow aggregate, forming a scattering center which DARKENS THE GLASS

Question 2

What happens when the light is removed?

Answer 2

~ Ag + CuI2 –> AgI + CuI (reverse reaction)

Question 3

What has this process been replaced by?

Answer 3

~ analogous processes in polycarbonate lenses