Question

on a sunny day when we enter a poorly lit room why we are not able to see for a while?

Answer 1

When we are in bright sunlight, the iris of our eyes adjust the pupil in such a way that less light enter our eyes (i.e. the pupil shrinks). But, when we enter a dark room, the iris needs to adjust the pupil in such a way that more light enter our eyes (i.e. the pupil needs to be enlarged). This is because we cannot see anything in a dark room if less light enter our eyes. The adjustment of pupil takes time. So, when we enter from bright sunlight to a dark room, we cannot see initially.