A student has difficulty in reading his textbooks but can read the blackboard clearly while sitting in the last row. Name the defect of vision the student is suffering from. List two reasons due to which this defect arises. Write the nature of the lenses required to correct this defect.
Generated by claude-sonnet-4-6 · 2026-06-15 06:52 · grounding rag
Model Answer
Defect: Myopia (near-sightedness) — the student can read the nearby textbook... wait, the student cannot read the textbook but can see the distant blackboard clearly. This is Hypermetropia (far-sightedness).
Two reasons:
- The focal length of the eye lens is too long.
- The eyeball has become too small.
Corrective lens: Convex (converging) lens of appropriate power.
Source: Chapter 10, Section 10.2 — Defects of Vision and Their Correction
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Explanation
- Re-read the clue carefully: difficulty reading textbooks (nearby) but sees blackboard (distant) clearly → Hypermetropia, not myopia. A common exam trap is to misread this.
- If the question said difficulty seeing the blackboard but can read the textbook, the answer would be Myopia + concave lens.
- Examiners expect the defect name, both causes (exactly as listed in the textbook), and the lens type — all three parts must be present for full marks.