A plano-convex lens is made of a material of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is:
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Question

A plano-convex lens is made of a material of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is:

G1 Physics · Accepted Answer

Step 1: For a plano-convex lens in air, 1/f = (μ − 1)(1/R − 0). Step 2: With μ = 1.6 and R = 60 cm, f = R/(μ − 1). Step 3: f = 60/0.6 = 100 cm. Final answer: (B) 100 cm.