Q 12-09-047JEE MainJEE Main 2026 (4 Apr, Shift 2)Easy
A convex lens is made from glass material having refractive index of $1.4$ with same radius of curvature on both sides. The ratio of its focal length and radius of curvature is ______.
Answer: (D) $1.25$
$\dfrac{1}{f} = (1.4 - 1)\left(\dfrac{1}{R} + \dfrac{1}{R}\right) = \dfrac{0.8}{R}$, so $\dfrac{f}{R} = \dfrac{1}{0.8} = 1.25$.
Solution by Sreeraj P, M.Sc Physics