Explain why a person with long-sightedness cannot see near objects clearly, and describe how a corrective lens fixes this problem.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A person struggles to read a book held at normal reading distance but can see distant objects clearly.
Model answer (5 marks)
In long‑sightedness the eyeball is too short or the lens cannot converge light sufficiently. Light from a near object is therefore focused behind the retina, giving a blurred image. A converging (convex) corrective lens is placed in front of the eye; it refracts the light rays inward before they enter the eye, so that the image is brought forward onto the retina and becomes clear.
Examiner tips
- Use the term "long‑sightedness" or "hyperopia". Explain the optical problem (focus behind retina). State that a convex lens is used and describe its effect (converges rays).
Common mistakes
- Confusing myopia with hyperopia. Forgetting to mention that the image is focused behind the retina. Using a diverging lens instead of a converging one.
Mark scheme (5 marks)
- In long-sightedness, the eyeball is too short (or the lens cannot converge light sufficiently)
- Light from a near object would be brought to a focus behind the retina
- The image on the retina is therefore blurred / not a sharp image
- A converging (convex) lens is used as the corrective lens
- The converging lens refracts light rays inward before they enter the eye, so that the image is brought forward onto the retina
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 →