Question

A convex lens of refractive index \(1.5\) and focal length \(f=18\) cm is immersed in water. The difference in focal lengths of the given lens when it is in water and in air is \( \alpha \times f \). Find the value of \( \alpha \). (Given: refractive index of water \(=\dfrac{4}{3}\))

Hint:

When a lens is immersed in a medium, always use the {relative refractive index} in the lens maker formula.

Answer 1

Correct Answer: 3