A person visits an optician and is diagnosed with short-sightedness. Explain why a person with short-sightedness cannot see distant objects clearly, and describe how a corrective lens restores clear vision.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
A person with short‑sightedness (myopia) has an eye that focuses parallel light rays from distant objects in front of the retina, because the eyeball is too long or the cornea/lens is too powerful (too curved). A diverging (concave) corrective lens is placed in front of the eye; it spreads the incoming rays out, causing them to diverge before entering the eye. This shifts the focal point back onto the retina, producing a sharp, clear image.
Examiner tips
- State the cause of myopia and the effect on image formation; mention the corrective lens type and its action; link the lens action to moving the focus onto the retina.
- Use the exact terms: ‘parallel light rays’, ‘in front of the retina’, ‘diverging lens’, ‘spread the rays out’, ‘focus back onto the retina’.
- Keep the answer concise and directly address each point in the mark scheme.
Common mistakes
- Confusing myopia with hyperopia or using a converging lens; describing the lens as ‘convex’ instead of ‘concave’; failing to explain that the lens spreads the rays before they enter the eye.
Mark scheme (5 marks)
- The eye focuses parallel (distant) light rays in front of the retina / before the retina
- This occurs because the eyeball is too long / the cornea or eye lens is too powerful (too curved)
- A diverging (concave) lens is used as the corrective lens
- The diverging lens spreads the rays out / causes the light to diverge before entering the eye
- This moves the focus back onto the retina, forming a sharp/clear image
Key terms in this question
Related
- All AQA A-Level Physics (7408) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →