Question

If you walk from a dark room into sunlight and back again into dark room, how would your pupils alter in size? What makes this happen?

Answer 1

Answer:

When you enter a bright place after being in a dark room, the pupil contracts, in order to protect your eyes due to sudden exposure of light.

This phenomenon is involuntary and is a defence mechanism. Then after sometimes, due to the phenomenon of bright light adaptation of human eyes we can see things normally in bright place.

The reverse thing happens while we enter a dark room from sunlight. Our pupil dilates in order to see things more clearly.

Answer 2

Answer:

When we go out into sunlight, we feel glare in our eyes as the pupil is large. ... On moving back from sunlight to a dark room again, we are not able to see the surroundings clearly, because the pupil is small. Gradually, the pupil expands, which then improves our vision.