1
Triple only
[1 mark]Which cells in the retina detect colour?
- Rod cells
- Cone cells
- Iris cells
- Lens cells
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Answer: B B (1)
2
Triple only
[3 marks]Describe the function of the cornea, the lens and the iris.
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- cornea: refracts / bends light entering the eye (1)
- lens: refracts light to focus it on the retina (1)
- iris: controls how much light enters the eye (1)
3
Triple only
[4 marks]A short-sighted person cannot see distant objects clearly. Explain why this happens and how it can be corrected.
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- light from distant objects is focused in front of the retina (1)
- because the eyeball is too long / the lens refracts the light too much (1)
- corrected with a concave lens (in glasses or contact lenses) (1) allow laser surgery to change the shape of the cornea
- which spreads the light out so that it focuses on the retina (1)
4
Triple only
[2 marks]Describe what a cataract is and how it can be treated.
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- the lens becomes cloudy, so less light reaches the retina (1)
- the lens is replaced with an artificial lens by surgery (1)
5
Triple only
[2 marks]Explain what causes colour blindness.
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- one or more types of cone cell are missing / not working properly (1)
- so the person has difficulty telling some colours apart, such as red and green (1)