Draw a labelled ray diagram showing how a concave lens corrects myopia in a person whose far point is closer than infinity. Your diagram must show the position of the image before and after correction.
Generated by claude-sonnet-4-6 · 2026-06-26 01:08 · grounding rag
Model Answer
Labelled Ray Diagram – Correction of Myopia using Concave Lens:
```
Without correction (myopic eye):
Distant object → Eye lens → Image formed IN FRONT of retina ✗
With correction:
Distant object → Concave lens → Diverged rays → Eye lens → Image ON retina ✓
```
Description of Diagram:
- A distant object (at infinity) sends parallel rays towards the eye.
- Before correction: The myopic eye converges these rays to a point in front of the retina (not on it), since the far point is closer than infinity.
- A concave (diverging) lens of suitable power is placed in front of the eye.
- After correction: The concave lens diverges the parallel rays such that they appear to come from the person's far point. The eye lens then focuses them exactly on the retina, forming a clear image.
Key labels required: Distant object, concave lens, eye lens, retina, image before correction (in front of retina), image after correction (on retina), far point.
Source: Chapter 10, Section 10.2(a) – Myopia
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Explanation
- Examiners expect an actual drawn diagram with all labels; describe it fully if drawing isn't possible in text.
- The three must-show elements for full marks: (1) image in front of retina without lens, (2) concave lens placed before the eye, (3) image shifted onto the retina after correction.
- Mention that the concave lens makes rays appear to diverge from the person's own far point — this is the key optical principle examiners reward.
- Do not use a convex lens; that corrects hypermetropia.