The magnitudes of power of a biconvex lens (refractive index 1.5) and that of a plano-concave lens (refractive index 1.7) are same. If the curvature of the plano-concave lens exactly matches with the curvature of the back surface of the biconvex lens, the

Question

The magnitudes of power of a biconvex lens (refractive index 1.5) and that of a plano-concave lens (refractive index 1.7) are same. If the curvature of the plano-concave lens exactly matches with the curvature of the back surface of the biconvex lens, then the ratio of radii of curvature of front and back surface of the biconvex lens is ______. [2026]

Smart Achievers · Accepted Answer

(2)

$| P_{A} |$ $=$ $| P_{B} |$

$0.5 (\frac{1}{R_{1}} + \frac{1}{R_{2}}) = \frac{0.7}{R_{2}}$

$\frac{5}{R_{1}} = \frac{2}{R_{2}}$

$\frac{R_{1}}{R_{2}} = \frac{5}{2}$

Solution

1 5 : 12

2 5 : 2

3 12 : 5

4 2 : 5

Ans.
(2)

$| P_{A} |$ $=$ $| P_{B} |$

$0.5 (\frac{1}{R_{1}} + \frac{1}{R_{2}}) = \frac{0.7}{R_{2}}$

$\frac{5}{R_{1}} = \frac{2}{R_{2}}$

$\frac{R_{1}}{R_{2}} = \frac{5}{2}$

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