MHT CET 2025 Physics question

Physics Ray Optics and Optical Instruments MHT CET 2025

A concave lens (refractive index = 1.5) has both surfaces of same radius of curvature R. If it is immersed in a liquid of refractive index 1.75 it will act as a

(A)concave lens of focal length (3.5) R
(B)concave lens of focal length 2 R
(C)convex lens of focal length (3.5) RCorrect
(D)convex lens of focal length 2 R

Answer: (C)

Solution

Lensmaker's formula in a medium: . For a double-concave lens , , so . In the liquid, , so . Then

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Question ID VK-102041