The radii of curvature for a thin convex lens are 10 cm and 15 cm...

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

Options

A1.2
B1.4
C1.5
D1.8

Correct answer

C. 1.5

Step-by-step 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}

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