An equi-concave lens is to be made of crown glass. What should be radii of the surfaces of the lens if the power of the lens is −2.5 dioptre and refractive index of crown glass is 1.65?
A
52m
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B
62cm
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C
52cm
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D
520cm
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Solution
The correct option is C52cm Given power of lens =−2.5D Power of lens =100f(cm) where f= focal length of the lens so −2.5=100ff=−10025f=−40cm