The diagram shows the eye of a cyclist entering a tunnel on a sunny day. Fig. 1 includes the iris, pupil and lens. The cyclist must see the road clearly as ...
Question 1 Report
The diagram shows the eye of a cyclist entering a tunnel on a sunny day. Fig. 1 includes the iris, pupil and lens. The cyclist must see the road clearly as the amount of light changes.
(a) Complete the sentence: the pupil is an opening in the __________. [1]
(b) Describe the pupil response as the cyclist moves from bright sunlight into the dark tunnel. [2]
(c) Explain how this response increases the amount of light reaching the retina. [2]
(d) Name the structure that forms an image on the retina by refracting light. [1]
Answer Details
(a) The pupil is an opening in the iris. [1]
(b) On entering the darker tunnel, the pupil becomes larger (dilates). [1] The iris muscles change the size of the opening to produce this response. [1]
(c) A larger pupil lets more light enter the eye. [1] Therefore, more light reaches the retina and its light-sensitive cells. [1]
(d) The lens refracts light to form an image on the retina. [1]
Exam point: The iris controls light entry by changing pupil diameter; the lens has the separate role of refracting light to focus an image.
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