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A person is suffering from myopic defect. He is able to see clear objects placed at `15 cm`. What type and of what focal length of lens he should use to see clearly the object placed `60 cm` away ?A. Concave lens of `20 cm` focal lengthB. Convex lens of `20 cm` focal lengthC. Concave lens of `12 cm` focal lengthD. Convex lens of `12 cm` focal length

Answer» Correct Answer - A
For viewing far objects, concave lenses are used and for concave lens
`u=` wants to see `=-60cm,v=` can see `=-15 cm`
so from `(1)/(f)=(1)/(v)-(1)/(u)impliesf=-20cm.`


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