My father’s lenses changes colour but mine does not.

I was having a question , why only  my father’s lens gets darken whenever he go out , but mine doesn’t. 

Then I came across a term called photo chromic lenses which   include transition lenses , light intelligent lenses , variable tint lenses . 

I went deep into   mechanism of photochromic lenses ,  then I came to  know the molecules which causes photochromic lenses to get darken on exposure to sunlight are activated by sun’s ultraviolet radiation.  

 

The glass  of these lenses acquire their photochromic properties through the embedding of microcrystalline silver halides (usually silver chloride) in a glass substrate. 

 

The lenses darken when exposed to UV light , but not in a normal artificial light .

They darken in less than one minute and continue to get dark in next 15 minutes. 

 

You should know that they follow a theory !  They get dark in cold weather condition . Hence they are temperature dependant .  Higher the temperature , lesser the dark the lenses be.

 

UV - A and UV - B  get filtered by the photochromic lenses most . 

 

They are available in all lens materials like polycarbonate, plastic , metal . And in lenses design like progressive lenses, bifocals , high index lenses. 

 

I am using  polycarbonate lenses and it provides  me great impact resistance than other materials I used  earlier .

 

So then I came to know my father used photochromic lenses  and mine one was not of that kind.

 

 

 

                   

                     #stayhome #staysafe