Question

A biconvex lens is having the radius of curvature of 10 cm and 15 cm. If focal length of the lens is 12 cm find refractive index of material of the lens.

(1) \(\frac{3}{2 }\)

(2) \(\frac{4}{3}\)

(3) 2

(4) \(\sqrt{3}\)

Answer 1

Correct option is:  (1) \(\frac{3}{2 }\)

\(\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)\)

\(\frac{1}{12} = (\mu - 1) \left( \frac{1}{10} \frac{1}{15} \right)\)

\(\mu - 1 = \frac{1}{2}\)

\(\mu = \frac{3}{2}\)