Question

1. With reference to he functioning of the eye, answer the questions that follow:
(a) What is meant by power of accommodation of the eye?
(b) What is the shape of the lens during (1) near vision (2) distant vision?
(c) Name the two structures in the eye responsible for bringing about the change in the shape of the lens.
(d) Name the cells of the retina and their respective pigments which get activated (1) in the dark and (2) in the light.

Answer 1

(a) Power of accommodation of the eye means the adjustment the eye makes to focus distant and close objects clearly. Hence by this property, the eye can see objects equally clear from a various distance.

(b) (1) The shape of the lens during near vision is more convex or rounded i.e., the ciliary muscles contract and squeeze the lens into a more convex shape. and thereby shorter focal length.

(2) The shape of the lens during distant vision is less convex or thin or flattened, i.e., the ciliary muscles relax and the lens returns to a flattering shape and thereby longer focal length.

(c)The two structures in the eye responsible for bringing about the change in the shape of the lens are:

(i) Ciliary muscles

(ii) Suspensory ligaments

(d) (1) The cell of the retina and the respective pigment which get activated in the dark is rod cells, and its pigment is rhodopsin

(2) The cell of the retina and the respective pigment which get activated in the light is cone cells, and its pigment is iodopsin.