Question

A hollow lens is made of thin glass and in the shape of a double concave lens. It can be filled with air, water of refractive index 1.33 or CS₂ of refractive index 1.6. It will act as a diverging lens, if it is

(a) filled with air and immersed in water

(b) filled with water and immersed in CS₂

(c) filled with air and immersed in CS₂

(d) filled with CS₂ and immersed in water

Answer 1

Answer is : (d) filled with CS₂ and immersed in water

When medium outside a lens is denser than medium of lens, then a concave lens will acts like a convex lens and vice-versa.

Now, when hollow lens is filled with CS₂ (η = 1.6) and immersed in water (η = 1.33), its nature remains diverging as refractive index of medium of lens is more than refractive index of surrounding medium.