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KCET · Physics · Ray Optics

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

  1. A \(400 \mathrm{~cm}\)
  2. B \(200 \mathrm{~cm}\)
  3. C \(100 \mathrm{~cm}\)
  4. D \(50 \mathrm{~cm}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(100 \mathrm{~cm}\)

Step-by-step Solution

Detailed explanation

Here, \(\frac{1}{\mathrm{f}}=(\mu-1)\left[\frac{1}{\mathrm{R}_{1}}-\frac{1}{\mathrm{R}_{2}}\right]\)
\(\frac{1}{f}=(1.6-1)\left[\frac{1}{60}-\frac{1}{\infty}\right]=\frac{1}{100}\)
\(\Rightarrow \quad \mathrm{f}=100 \mathrm{~cm}\)