The radii of curvature of the surfaces of a double convex lens are `20 cm and 40 cm` respectively, and its focal length is `20 cm`. What is the refractive index of the material of the lens ?

Explanation

To find the refractive index of the material of the double convex lens, we can use the lens maker's formula:

\[ \frac{1}{F} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \]

where:
- \( F \) is the focal length of the lens,
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