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A convex lens is made of a glass of refr...

A convex lens is made of a glass of refractive index 1.5. The radius of curvature of each of its surfaces is 20 cm. Then the ratio of the power of the lens when placed in air to its power when immersed inside a liquid of refractive index 1.25 is

A

`2 : 5`

B

`5 : 2`

C

`3 : 2`

D

`2 : 3`

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