(A) (i) How does the change in curvature of the eye lens help us in the process of seeing nearby objects clearly?

(ii) State the range of the power of accommodation of a normal human eye.

OR

(B) Draw a ray diagram to show the correction of eye defect of an old man who cannot see an object placed closer than $1\text{ m}$ from his eye, clearly.

This is an internal-choice question; either sub-part may be attempted.

Part (A): The chapter explains under 'Power of Accommodation' (Section 10.1.1) that the eye lens is made of a fibrous, jelly-like material whose curvature is modified by the ciliary muscles. 'When you are looking at objects closer to the eye, the ciliary muscles contract. This increases the curvature of the eye lens. The eye lens then becomes thicker. Consequently, the focal length of the eye lens decreases. This enables us to see nearby objects clearly.' This is the ability called accommodation. The text further defines the operating range: 'a normal eye can see objects clearly that are between 25 cm and infinity' — the near point (25 cm) to the far point (infinity) — which is the range over which the power of accommodation operates for a normal human eye.

Part (B): The old man cannot see objects closer than $1\text{ m}$, meaning his near point has receded from the normal $25\text{ cm}$ to $1\text{ m}$ — exactly the condition described in the chapter for hypermetropia/presbyopia: 'The near point, for the person, is farther away from the normal near point (25 cm).' As per Section 10.2(b), 'This defect can be corrected by using a convex lens of appropriate power... Eye-glasses with converging lenses provide the additional focussing power required for forming the image on the retina.' The ray diagram must show a convex lens producing a virtual, erect image of an object placed at the normal near point (25 cm) at the person's actual near point (1 m), consistent with Fig. 10.3(c) of the chapter showing correction for hypermetropia.