Refractive index of a glass convex lens is 1.5 . The radius of curvature of each of the two surfaces of the lens is 20 ~cm . The ratio of the power of the lens when immersed in a liquid of refractive index 1.25 to that when placed in air is

Step-by-step solution

Given data: _ g =1.5, R ₁= R ₂=20 ~cm , _l=1.25 aligned P ₁= ( _ g _ a -1 ) ( 1 R ₁ - 1 R ₂ ) & =(1.5-1) ( 1 R ₁ - 1 R ₂ ) P ₂= ( _ g _l -1 ) ( 1 R ₁ - 1 R ₂ ) & = ( 1.5 1.25 -1 ) ( 1 R ₁ - 1 R ₂ ) & =(1.2-1) ( 1 R ₁ - 1 R ₂ ) aligned Taking ratio, P ₂ P ₁ = 1.2-1 1.5-1 = 2 5