Question

A convex lens of glass of refractive index is immersed in a medium of refractive index and how will the lunch there really closing time

Answer 1

The ability of a lens to act as converging or diverging depends upon its refractive index. The refractive index n of the material of a lens depends upon the medium in which the lens is placed. Generally the lens is in air so n gives refractive index of material of lens with respect to air. If you place the convex lens in a medium other than air, then due to change in n, the focal length f of lens changes. if n decreases, f increases.