Q1. [2] § 10.2 DEFECTS OF VISION AND THEIR CORRECTION
When do we say that a particular person is suffering from hypermetropia ? List two causes of this defect. Name the type of lens used to correct this defect.
Previously asked in CBSE board exam
2024 31/3/1 Q24
Generated by claude-sonnet-4-6 · 2026-06-15 06:54 · grounding rag
Model Answer
A person is said to suffer from hypermetropia when they can see distant objects clearly but cannot see nearby objects distinctly (near point is farther than 25 cm).
Two causes:
- The focal length of the eye lens is too long.
- The eyeball has become too small, so light from nearby objects is focused behind the retina.
Correction: A convex lens (converging lens) of appropriate power is used.
Source: Chapter 10, Section 10.2 – Defects of Vision and their Correction
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Explanation
- The question has three parts (condition, causes, correction) but is only 2 marks — keep it brief and avoid excess detail.
- Examiners look for: the key symptom (cannot see nearby clearly), exactly two causes (focal length too long / eyeball too small), and the correct lens type (convex/converging).
- Do not confuse with myopia (concave lens). Hypermetropia = far-sighted = convex lens.
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