Question

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
• C. 1.5
• D. 1.8

Hint:

Use the lensmaker's formula to relate the focal length, radii of curvature, and refractive index of the lens material.

Answer 1

The Correct Option is C

\( \frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \) \( \frac{1}{12} = (\mu - 1) \left( \frac{1}{10} - \frac{1}{-15} \right) \) \( \frac{1}{12} = (\mu - 1) \left( \frac{3+2}{30} \right) \) \( \mu = \frac{3}{2} \)