A plano convex lens (μ = 1.5) has a maximum thickness of 1 mm. If diameter of its aperture is 4 cm. Find (i) Radius of curvature of curved surface; (ii) its focal length in air.
Options

Question

A plano convex lens (μ = 1.5) has a maximum thickness of 1 mm. If diameter of its aperture is 4 cm. Find (i) Radius of curvature of curved surface; (ii) its focal length in air.

G1 Physics · Accepted Answer

Derived solution: Step 1: For paraxial refraction at a spherical surface use n₂/v - n₁/u = (n₂ - n₁)/R, applying the Cartesian sign convention at each surface. Step 2: Substitute the values given in the question and apply the geometry/sign convention shown. Step 3: On simplification the result is R = 0.2 m; f = 0.4 m. Therefore the correct option is B.