Q 12-09-089JEE MainJEE Main 2024 (6 Apr, Shift 2)Easy
For a thin convex lens, the radii of curvature are $15\ \text{cm}$ and $30\ \text{cm}$ respectively. The focal length of the lens is $20\ \text{cm}$. The refractive index of the material is
Answer: (C) $1.5$
For a biconvex lens, $R_1 = +15\ \text{cm}$, $R_2 = -30\ \text{cm}$:
$$\frac{1}{20} = (\mu - 1)\left(\frac1{15} + \frac1{30}\right) = (\mu - 1)\times\frac{1}{10} \Rightarrow \mu = 1.5$$
Solution by Sreeraj P, M.Sc Physics