A biconvex lens has radii of curvature 20 cm each. If the refractive index of the material of the lens is 1.5, the power of the lens is:
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A biconvex lens has radii of curvature 20 cm each. If the refractive index of the material of the lens is 1.5, the power of the lens is:

G1 Physics · Accepted Answer

Step 1: Lens-maker formula P = (μ − 1)(1/R₁ − 1/R₂), using radii in metres. Step 2: R₁ = +0.20 m, R₂ = −0.20 m, μ = 1.5. Step 3: P = 0.5(1/0.20 + 1/0.20) = 0.5 × 10 = +5 dioptres. Final answer: (C) +5 D.