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:
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Question

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:

Select all that apply

G1 Physics · Accepted Answer

For a thin lens in a medium, power P = [n(glass)/n(L) − 1](1/R₁ − 1/R₂). Here n(glass) = 1.5 and R₁ = +0.20 m, R₂ = −0.20 m, so P = 10[1.5/n(L) − 1] D. Thus P decreases with n(L), becomes zero at n(L) = 1.5, is positive below 1.5 and negative above 1.5. The source key accepts A or B.