Question

A lens behaves as a converging lens in air and diverging lens in water. The refractive index of the material of the lens is

• A. equal to that of water
• B. less than that of water
• C. greater than that of water
• D. Nothing can be predicted

Answer 1

Answer: (B)

less than that of water

Answer 2

If a lens (made of glass) of refractive index $\mu_{g}$ is immersed in a liquid of refractive index $\mu_{l}$, then its focal length in liquid $f_{l}$ is given by $\frac{1}{f_{l}}=\left(_{l} \mu_{g}-1\right)\left[\frac{1}{R_{1}}-\frac{1}{R_{2}}\right]\,\,\,\, ...(i)$ If $\mu_{g}