Generated by claude-sonnet-4-6 · 2026-06-15 06:53 · grounding rag
Model Answer
(i) The defect is Myopia (Short-sightedness).
Reason: In the diagram, the image is formed in front of the retina instead of on it, which is the characteristic feature of myopia.
(ii) Two causes of myopia:
- Excessive curvature (increased converging power) of the eye lens.
- Elongation of the eyeball (increase in the length of the eyeball).
(iii) Myopia is corrected by using a concave (diverging) lens of suitable power. It diverges the incoming rays so that they finally converge on the retina.
Corrective diagram:
```
Object → [Concave lens] → Eye lens → Image forms ON retina
```
(Diagram shows diverging rays from concave lens entering the eye and converging exactly on the retina.)
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Explanation
- The key visual clue is the image forming before the retina — this uniquely identifies myopia. Always state this reason explicitly.
- For causes, examiners expect the two standard textbook reasons: increased lens curvature AND elongated eyeball.
- For the correction diagram, draw the concave lens in front of the eye, show diverging rays, and label that the final image falls on the retina. Even a rough labelled sketch earns marks.
- Marks split: (i) 1 mark — name + reason; (ii) 1 mark — any two causes; (iii) 1 mark — correct lens named + diagram.