Q7. Answer briefly:
(c) How does the eye regulate the amount of light that falls on the retina.
Light enters the eye through the pupil, an aperture present in the centre of the iris. The iris has two types of muscles-circular smooth muscles and radial smooth muscles-which regulate the amount of light that falls on the retina. The smooth circular muscles contract in bright light which makes the pupil smaller in size; hence, a lesser amount of light falls on the retina. In dim light, the pupil is widened by the contraction of radial smooth muscles so that a sufficient amount of light falls on the retina.