In a long glass tube, mixture of two liquids A and B with refractive indices 1.3 and 1.4 respectively, forms…
- $\frac{1}{3} \mathrm{~cm}$
- $\frac{4}{3} \mathrm{~cm}$
- $1\mathrm{~cm}$
- $\frac{2}{3} \mathrm{~cm}$
Solution

$\begin{aligned} & \frac{\mathrm{n}_2}{\mathrm{v}}-\frac{\mathrm{n}_1}{\mathrm{u}} \frac{\mathrm{n}_2-\mathrm{n}_1}{\mathrm{R}} \\ & \frac{1.4}{\mathrm{v}}-\frac{1.3}{-13}=\frac{0.1}{\mathrm{R}} \\ & \frac{1.4}{\mathrm{v}}=\frac{1-\mathrm{R}}{10 \mathrm{R}} \\ & \frac{1.4}{\mathrm{v}}=\frac{1-\mathrm{R}}{10 \mathrm{R}} \\ & \mathrm{m}=\frac{\mathrm{v} / \mathrm{n}_2}{\mathrm{u} / \mathrm{n}_1} \\ & -2 \times \frac{(-13)}{1.3}=\frac{10 \mathrm{R}}{1-\mathrm{R}} \\ & \mathrm{R}=\frac{2}{3} \mathrm{~cm}\end{aligned}$
Asked in: JEE Main 2025 (28 Jan Shift 2)