An eye scanner uses parallel light rays to test a person's distance vision. The retina is 24.0 mm behind the cornea.
The table shows the predicted position where the rays focus with different spectacle lenses.
| Spectacle lens | Distance of focus behind the cornea in mm |
|---|---|
| none | 22.8 |
| P | 21.5 |
| Q | 24.0 |
| R | 25.6 |
Explain which spectacle lens should be used to correct the person's vision. Include the shape of the lens in your answer.
102 exam-style questions on Edexcel GCSE Biology 2.4 The eye, covering 2.4.1 Structure and function of the eye and 2.4.2 Eye defects and their correction. Each one has a worked solution and a mark scheme showing where the marks go.