Q65 / 75 · JEE Main 2025 (3 Apr Shift 1) · Physics

The radii of curvature for a thin convex lens are 10 cm and 15 cm respectively. The focal length of the lens is 12 cm. The refractive index of the lens material is

  • A
    1.2
  • B
    1.4
  • Correct answer
    C
    1.5
  • D
    1.8

Solution

$\begin{aligned} & \frac{1}{\mathrm{f}}=(\mu-1)\left(\frac{1}{\mathrm{R}_1}-\frac{1}{\mathrm{R}_2}\right) \\ & \frac{1}{12}=(\mu-1)\left(\frac{1}{10}-\frac{1}{-15}\right) \\ & \frac{1}{12}=(\mu-1)\left(\frac{3+2}{30}\right) \\ & \mu=\frac{3}{2}\end{aligned}$

Hence, the correct answer is option: 'C'.

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