Science — CBSE Class 10 board question

(i) With age, the ciliary muscles weaken and the flexibility of the eye lens diminishes. This reduces the eye's ability to adjust its focal length (power of accommodation decreases), making it difficult to see both nearby and distant objects clearly.

(ii) The defect is called Presbyopia.

(iii) Such a person requires bi-focal lenses — upper part concave (for distant vision) and lower part convex (for near vision).

Ray diagram (Convex lens correcting near vision):

```
Object Convex lens Eye
| | \ |
---- rays ----( )-----> [Retina]
| /
```
(Convex lens converges rays so image forms on retina instead of behind it.)

Source: Chapter 10, Section 10.2(c) — Presbyopia

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• (i) Always link the cause to ciliary muscles weakening + lens flexibility reducing — both points may be needed for full credit.
• (ii) The specific name Presbyopia is expected; writing only "old age defect" is insufficient.
• (iii) For the ray diagram, examiners look for: a convex lens, rays converging onto the retina, and labelling. Since the question says "type of corrective lens," a single clear diagram of the convex lens (near vision correction) with labels is acceptable. Mention bi-focal if space permits.