Fig. 1 shows an optician's test set-up. A person with normal vision looks at a distant sign through a transparent lens. The lens can be moved into position ...
Question 1 Report
Fig. 1 shows an optician's test set-up. A person with normal vision looks at a distant sign through a transparent lens. The lens can be moved into position in front of the eye.
(a) Name the part of the human eye that changes shape to focus light from the sign. [1]
(b) Describe what happens to the lens of a normal eye when the person changes from viewing the distant sign to reading a book held 25 cm away. [2]
(c) Explain why a convex lens may help a person who is long-sighted read small print. [3]
(d) Draw a line on Fig. 1 to show the path of one ray of light after it passes through the convex lens. [2]
Answer Details
(a) The part that changes shape to focus light is the eye lens. [1]
(b) When changing from a distant sign to a book 25 cm away, the lens becomes thicker or more curved. It then refracts the diverging rays from the near object more strongly. [2]
(c) In long-sightedness, light from a nearby object would be focused behind the retina. A convex lens converges the rays before they enter the eye, bringing the image forwards onto the retina. [3]
(d) After passing through a convex lens, a ray bends towards the principal axis and continues towards the retina at the back of the eye. The required path is shown below. [2]
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