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Question:

What is the refractive index of the material of a plano-convex lens, if the radius of curvature of the convex surface is 10 cm and focal length of the lens is 30 cm?

1

13

43

23

Solution:

From the lens maker's formula, 1/f = (μ-1)(1/R1 - 1/R2) => 1/30 = (μ-1)(1/10 - 1/∞) => μ-1 = 1/3 => μ = 4/3