A biconvex lens of glass (μ = 1.5) has radii of curvature 20 cm and 30 cm. Its focal length is

(B) 24 cm. (1)/(f) = (μ - 1)((1)/(R_1) - (1)/(R_2)) = 0.5((1)/(20) + (1)/(30)) = (1)/(24), so f = 24 cm.

Ray Optics and Optical Instruments question for NEET / JEE Main, with solution

Q 12-09-027NEETJEE MainMedium

A biconvex lens of glass ($\mu = 1.5$) has radii of curvature $20$ cm and $30$ cm. Its focal length is