MPSC State Service 2017 · GS · Question 53 of 100

What is the focal length of a double convex lens for which the radius of curvature of each surface is 50 cm and the refractive index of glass is 1.50?

Physics

Answer: C. 50 cm

For a double convex lens with R = 50 cm and μ = 1.5: 1/f = (μ−1)(2/R) = 0.5 × 2/50 = 1/50, so f = 50 cm.

Source: MPSC Rajyaseva Prelims 2017 GS Paper I (official paper)

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