Question 1
Which part of the eye has no light receptors because the optic nerve leaves the eye there?
- Pupil
- Cornea
- Blind spot
- Iris
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Answer: C (1)
Question 2
State the function of each of these parts of the eye. (a) cornea [1] (b) iris [1] (c) lens [1] (d) optic nerve [1]
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- (a) refracts light (1) allow bends light / begins to focus light
- (b) controls how much light enters the pupil / eye (1) ignore controls the size of the pupil unless linked to light
- (c) focuses light on to the retina (1)
- (d) carries impulses to the brain (1) allow electrical signals; reject carries images / light / messages to the brain
Question 3
A person walks from a dim room into bright sunlight. Explain what happens to the pupil.
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- the pupil gets smaller / diameter decreases / constricts (1)
- so less light enters the eye (1)
- this protects the retina from damage (1) allow reflex is automatic / rapid
Question 4
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanExplain how the muscles in the iris cause the pupil to become wider in dim light.
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- radial muscles contract (1)
- circular muscles relax (1)
- the muscles are antagonistic / work against each other (1)
- so pupil diameter increases / pupil dilates and more light enters the eye (1)
Question 5
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanA person looks at a near object. Which row shows what happens in the eye?
- ciliary muscles contract; suspensory ligaments slack; lens thicker
- ciliary muscles contract; suspensory ligaments tight; lens thinner
- ciliary muscles relax; suspensory ligaments slack; lens thicker
- ciliary muscles relax; suspensory ligaments tight; lens thinner
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Answer: A (1)
Question 6
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanA person looks at a book, then looks up at a tree far away. Explain how the eye changes to focus on the tree.
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- ciliary muscles relax (1)
- tension in the suspensory ligaments increases / ligaments pulled tight (1) reject suspensory ligaments contract / relax
- lens becomes thinner / less curved (1)
- light is refracted less (1)
- light is focused on the retina (1)
Question 7
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels mean(a) State the function of the fovea. [1] (b) Rods and cones are light receptors in the retina. Explain why it is difficult to see colours in very dim light. [3] (c) Describe the distribution of rods and cones in the human retina. [2]
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- (a) gives the sharpest vision / vision in the greatest detail (1) allow area with the highest density of cones
- (b) colour vision depends on cones (1)
- (b) there are three kinds of cone absorbing light of different colours (1)
- (b) cones are less sensitive to light than rods / rods are used for night vision (1) allow cones do not work in dim light
- (b) rods do not give colour vision / there is only one type of rod (1)
- (b) Max 3
- (c) cones are concentrated in the fovea (1)
- (c) rods are spread over the rest of the retina, more towards the edges / there are no rods in the fovea (1) ignore no receptors at the blind spot