A double convex lens made of glass of refractive index 1.5 and radii of curvature of the curved surfaces 20 cm each is immersed in a liquid of refractive index n_L . The correct plot showing the variation of the power, in the units of diopter (D) , as a function of n_L is:

Step-by-step solution

The focal length f of a lens immersed in a medium of refractive index n_L is given by the Lens Maker's formula: 1 f = ( n_g n_L - 1 ) ( 1 R₁ - 1 R₂ ) Given that the lens is double convex, the radii of curvature are R₁ = +20 cm = +0.2 m and R₂ = -20 cm = -0.2 m . The refractive index of the glass is n_g = 1.5 . Substituting these values into the formula gives: 1 f = ( 1.5 n_L - 1 ) ( 1 0.2 - 1 -0.2 ) 1 f = ( 1.5 n_L - 1 ) (5 + 5) = 10 ( 1.5 n_L - 1 ) The power P of the lens is defined as the reciprocal of its focal