Science
Study the diagram given below and answer the questions that follow :
(a) Name the defect of vision represented in the diagram. Give reason for your answer.
(b) List two causes of this defect.
(c) With the help of a diagram show how this defect of vision is corrected.
Answer
(a) The defect of vision shown in the diagram is Hypermetropia (long-sightedness).
Explanation : In the diagram, the rays of light coming from a near object (point N) converge to form the image behind the retina instead of on it which means the person can see distant objects clearly but cannot see nearby objects distinctly.
(b) Causes hypermetropia defect:
- The eyeball is too short, so the retina is closer to the eye lens.
- The focal length of the eye lens is too long (the lens becomes less convex), so it cannot bend light rays sufficiently to form the image on the retina.
(c) Hypermetropia is corrected by using a convex (converging) lens which converges the incoming light rays before they enter the eye so that they can be focused exactly on the retina.
Diagram showing correction for hypermetropic eye is given below :
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