…how does those glasses become shaded when foing into the sun and then once indoors or in shade they become clear again? What makes them do that?
In: 1
Tiny molecules of silver halide and chloride are embedded within a photochromic lens which is invisible and clear until exposed to sunlight/UV rays.
A chemical process takes place when exposed to sunlight/UV and the molecules effectively move, change shape and absorb the light. This process changes the molecules and they darken to a sunglasses shade/tint.
The photochromic lens will remain in this ‘darkened’ sunglasses state whilst exposed to sunlight/UV and the molecules will reverse the process once the lenses are removed from the sunlight/UV rays returning to the original ‘transparent/clear’ lens.
https://www.onlineopticiansuk.com/photochromic-lenses-explained-i149
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