State reasons for Myopia. With the help of ray diagrams, show the
(a) image formation by a myopic eye, and
(b) correction of myopia using an appropriate lens.
Generated by claude-sonnet-4-6 · 2026-06-15 06:54 · grounding rag
Model Answer
Causes of Myopia:
Myopia arises due to:
- Excessive curvature of the eye lens, or
- Elongation of the eyeball.
(a) Image formation by a myopic eye:
In a myopic eye, the image of a distant object is formed in front of the retina instead of on it.
```
Distant object → Eye lens → Image (formed in front of retina) ✗ Retina
```
(Ray diagram: parallel rays from distant object converge before the retina)
(b) Correction of myopia:
A concave lens of suitable power is used. It diverges the incoming rays so that they converge exactly on the retina.
```
Distant object → Concave lens → Eye lens → Image (on retina) ✓
```
(Ray diagram: concave lens diverges rays; eye lens then focuses them onto the retina)
Source: The Human Eye and the Colourful World, Section 10.2
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Explanation
- The question is 3 marks: ~1 mark for causes, ~1 mark for each diagram (described/drawn). Keep causes brief (2 points) and diagrams clearly labelled.
- Since this is a written exam, draw actual ray diagrams on paper with labels: "Retina," "Eye lens," "Image," and for correction — "Concave lens." The examiner specifically looks for the image forming in front of the retina (myopia) and on the retina (after correction).
- Never confuse myopia correction (concave lens) with hypermetropia correction (convex lens).