A thin plano-convex lens acts like a concave mirror of focal length 0 . 2 m , when silvered on its plane surface. The refractive index of the material of the lens is 1 . 5 . The radius of curvature of the convex surface of the lens will be

Question

A thin plano-convex lens acts like a concave mirror of focal length 0 . 2 m , when silvered on its plane surface. The refractive index of the material of the lens is 1 . 5 . The radius of curvature of the convex surface of the lens will be, 0 . 1 m, 0 . 2 m, 0 . 4 m, 0 . 8 m

MARKS App · Accepted Answer

F = - 0.2 m , f m = ∞ μ = 1.5 f l = R μ - 1 , 1 f F = 1 f m - 2 f l ⁡ ⇒ F = - f l ⁡ 2 ⇒ F = - R 2 μ - 1 ∴ - 0.2 = - R 2 1.5 - 1 ∴ 0.2 = R 1 ∴ R = 0.2 m

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