Science — CBSE Class 10 board question

(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:

1. Excessive curvature (increased converging power) of the eye lens.
2. 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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• 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.