If the refractive index from air to glass is 3 2 and that from air to water is 4 3 , then the ratio of focal lengths of a glass lens in water and in air is

Step-by-step solution

Given, refractive index from air to glass, _ a _ g = 3 2 Refractive index from air to water, _ a _ w = 4 3 Using lens Maker's formula, aligned 1 f &= ( ₁ ₂-1 ) ( 1 R₁ - 1 R₂ ) f_ water f_ air &= ( _ a _ g -1 ) ( _ w _ g -1 ) = ( _ a _ g -1 ) ( _ a _ g _ a _ w -1 ) &= ( 3 2 -1 ) ( 3 2 ) = 1 2 8 1 = 4 1 or 4: 1 aligned