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Question: Answered & Verified by Expert
A plano-convex lens is made of refractive index of 1.6. The radius of curvature of the curved surface is $60 \mathrm{~cm}$. The focal length of the lens is
PhysicsRay OpticsKCETKCET 2010
Options:
  • A $400 \mathrm{~cm}$
  • B $200 \mathrm{~cm}$
  • C $100 \mathrm{~cm}$
  • D $50 \mathrm{~cm}$
Solution:
1292 Upvotes Verified Answer
The correct answer is: $100 \mathrm{~cm}$
Here, $\frac{1}{\mathrm{f}}=(\mu-1)\left[\frac{1}{\mathrm{R}_{1}}-\frac{1}{\mathrm{R}_{2}}\right]$
$\frac{1}{f}=(1.6-1)\left[\frac{1}{60}-\frac{1}{\infty}\right]=\frac{1}{100}$
$\Rightarrow \quad \mathrm{f}=100 \mathrm{~cm}$

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