CBSE Class 10 Science 2019 · Paper 31/1/2 · Question 5
Write the structure of eye lens and state the role of ciliary muscles in the human eye.
Answer
A transparent, biconvex, jelly-like lens; the ciliary muscles change its curvature and focal length to focus near and distant objects.
Structure: the eye lens is a transparent, convex (biconvex) lens made of a fibrous, jelly-like material. It is held in position behind the pupil by suspensory ligaments attached to the ciliary muscles.
Role of the ciliary muscles: they change the curvature of the eye lens and hence its focal length (the power of accommodation). When they relax, the lens becomes thin and its focal length increases, so distant objects are seen clearly; when they contract, the lens becomes thicker and its focal length decreases, so nearby objects are seen clearly.
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