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The focal length of a plano-convex lens ...

The focal length of a plano-convex lens is `f` and its refractive index is 1.5 it is kept over a plane galss plate with its curved surface touching the glass plate. The gap between the lens and the glass plate is filled by a liquid. As a result the effective focal length of the combination becomes `2f`. Then the refractive index of the liquid is

A

1.5

B

2

C

1.25

D

1.33

Text Solution

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The correct Answer is:
C
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