NDA 2017 Physics question

The radii of curvature of the faces of a double convex lens are 10 cm and 20 cm. The refractive index of the glass is 1·5. What is the power of this lens (in units of dioptre) ?

(A)+7·5 DCorrect
(B)–7·5 D
(C)+2·5 D
(D)+5·0 D

Answer: (A)

Solution

By the lens maker's formula, for a double convex lens. With the radii in metres: $P =

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Question ID VK-030747