A double convex lens has power P and same radii of curvature R of both the surfaces. The radius of curvature of a surface of a plano-convex lens made of the same material with power 1.5 P is :
Solution
Assume refractive index = $\mu$<sub>$l$</sub>
<br><br>P = $\left( {{\mu _l} - 1} \right)\left( {{2 \over R}} \right)$ .....(1)
<br><br>${3 \over 2}P = \left( {{\mu _l} - 1} \right)\left( {{1 \over {{R_1}}}} \right)$ ......(2)
<br><br>from (1)/(2)
<br><br>$${P \over {{3 \over 2}P}} = {{\left( {{2 \over R}} \right)} \over {\left( {{1 \over {{R_1}}}} \right)}}$$
<br><br>$\Rightarrow$ R<sub>1</sub> = ${R \over 3}$
About this question
Subject: Physics · Chapter: Optics · Topic: Reflection and Mirrors
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