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Defects of Vision and Their Correction

A girl viewed...

Question

A girl viewed an object and found that it is not clearly visible to her. It was found that the image was formed by her eye lens $3 c m$ away from the pupil of her eyes.The girl can correct this defect by using a:

A

concave lens

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B

convex lens

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C

bi-focal lens

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D

plano-convex lens

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Solution

The correct option is D convex lens
Since the distance between pupil and retina is $2.3 c m$ and the image formed is at a distance of $3 c m$ from the pupil, it is obvious that the image is formed behind the retina.
This defect is known as hyper-metropia which happens because converging power of eyes lens reduces
So to correct this defect of vision, the girl needs to use a convex lens. It will form the image at the retina by increasing the combined power.

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