Question

Write about your experience in the following two cases.
a. Enter into a dark room from a very bright place. What happens?
b. Sit in a dark room for some time and go into a bright light room. What happens?

Answer 1

a) When we enter into a dark room from a very bright place, we experience difficulty in vision. This change is due to regeneration of rhodopsin, the pigment of the rods, which was earlier broken down due to bright light and even the size of the pupil is less in the bright light. After sometimes the vision gets restored by regeneration of rod cells and dilation of the pupil in the dark which permits more light to enter the eyes. Rod cells are the cells which help in dim light vision.

b) Sit in a dark room for some time and go into a bright light room will cause glare to eyes and cause discomfort in vision as in a dark room the pupil gets dilated so suddenly when exposed to bright light, a large amount of light enters the pupil which causes glare, it is further regulated by ciliary muscle and the size of pupil gets reduced. The sudden switch from dark room to a bright light room can cause discomfort in vision as in dark the cone cells are bleached which takes time to regenerate when exposed to light.