(A) Observe the following diagram and answer the questions following it :
(i) Identify the defect of vision shown.
(ii) List its two causes.
(iii) Name the type of lens used for the correction of this defect.
Generated by claude-sonnet-4-6 · 2026-06-15 06:52 · grounding rag
Model Answer
(i) The defect shown is Myopia (near-sightedness). The image is formed in front of the retina instead of on it.
(ii) Two causes:
- Excessive curvature of the eye lens.
- Elongation of the eyeball.
(iii) A concave lens (diverging lens) of suitable power is used to correct myopia.
Source: Chapter 10, Section 10.2(a) – Myopia
---
Explanation
- The diagram shows rays converging in front of the retina → this is the key identifier for myopia (not hypermetropia, where image forms behind the retina).
- Examiners specifically look for both causes stated clearly; missing one costs a mark.
- "Concave lens" must be named — writing only "diverging lens" may lose the mark if the term is not recognised as equivalent.
- This 2-mark question typically awards: 1 mark for defect + causes combined, 1 mark for corrective lens — so be concise and precise.