Q 12-09-183JEE MainJEE Main 2020 (8 Jan, Shift 1)Easy
A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is $30$ cm and the refractive index of the lens material is $1.5$. Then the focal length of the lens (in cm) is ______.
Numerical value type. Enter your answer.
Answer: 60
$$\frac1f = (\mu - 1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right) = 0.5\left(\frac{1}{30} - 0\right) \Rightarrow f = 60\ \text{cm}$$
Solution by Sreeraj P, M.Sc Physics