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AP EAMCET · PHYSICS · Ray Optics

The radius of curvature of a convex lens is \(40 \mathrm{~cm}\), for each surface. Its refractive index is 1.5 . Its focal length is

  1. A \(40 \mathrm{~cm}\)
  2. B \(20 \mathrm{~cm}\)
  3. C \(80 \mathrm{~cm}\)
  4. D \(30 \mathrm{~cm}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(40 \mathrm{~cm}\)

Step-by-step Solution

Detailed explanation

From the formula \(\begin{aligned} & \frac{1}{\mathrm{f}}=(\mu-1)\left(\frac{1}{\mathrm{R}_1}-\frac{1}{\mathrm{R}_2}\right) \\ & \frac{1}{\mathrm{f}}=(1.5-1)\left(\frac{2}{40}\right)=\frac{1}{40}\end{aligned}\) focal length, \(f=40 \mathrm{~cm}\)