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The radius of curvature of the curved su...

The radius of curvature of the curved surface of a plano-convex lens is `20 cm`. If the refractive index of the material of the lens be `1.5`, it will

A

act as a convex lens only for the objects that lie on its curved side.

B

act as a concave lens for the objects that lie on its curved side.

C

act as a convex lens irrespective of the side on which the object lies.

D

act as a concave lens irrespective of side on which the object lies.

Text Solution

Verified by Experts

The correct Answer is:
C
As we know the relations between `f,mu , R_1 and R_2` is known as lens : maker.s formula
`1/f = (mu - 1)(1/(R_1) - 1/(R_2))`
`R = oo, R_2 = R`
`f = (R)/((mu - 1))`
Given that,
`R = 20 cm`,
`mu = 1.5`
Put the values
`f = R/(mu - 1) = 20/(15 - 1) = 40 cm`
As `f gt 0` , it mean converging nature of the lens.
So, lens actas a convex lens irrespective of the. side on which the object lies.
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