Correct Option: D

We need light to see what is around us and to see colour. Light bounces off the objects we look at. These reflect different amounts of light which we see as different colours. Our eyes need light to work. Light entering the eye is collected by the retina and processed by the brain to obtain the pictures that we need to see. Light is an essential part of this process, for example it is difficult to read when light levels are low. Sometimes light can cause problems for our vision. Usually our eyes adjust to the new source of light and we are able to see clearly again after a few seconds. The eye adjusts to the new level of light by making our pupil smaller (constricting). When a person walking in bright light enters a dark room, he is not able to see clearly because the iris is unable to dilate the pupil immediately. This phenomenon is called as photophobia.