Question

Protocromatic lenses darken in sunlight but not indoors under artificial light. Why? ​

Answer 1

Explanation:

The molecules that cause photochromic lenses to darken are stimulated by UV rays from sun. On exposure to ultraviolet light, the lenses darken to mimic sunglasses. These changes in lens optimise the eyesight. The lenses do not darken in artificial indoor light because it happens only in response to the short wavelengths of sunlight.