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NEET · Physics · STD 12 - 9. Ray optics and optical instruments

A double convex lens has focal length \(25\; \mathrm{cm}\). The radius of curvature of one of the surfaces is double of the other. Find the radii If the refractive index of the material of the lens is \(1.5 \)

  1. A \(100 \;\mathrm{cm}, 50\; \mathrm{cm}\)
  2. B \(25\; \mathrm{cm}, 50\; \mathrm{cm}\)
  3. C \(18.75\; \mathrm{cm}, 37.5 \;\mathrm{cm}\)
  4. D \( 50\; \mathrm{cm}, 100\; \mathrm{cm}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(18.75\; \mathrm{cm}, 37.5 \;\mathrm{cm}\)

Step-by-step Solution

Detailed explanation

\(\frac{1}{f}=\left(\frac{\mu_{2}-\mu_{1}}{\mu_{1}}\right)\left(\frac{1}{R_{1}}-\frac{1}{R_{2}}\right)\) \(\Rightarrow \frac{1}{25}=\left(\frac{1.5-1}{1}\right)\left(\frac{1}{R}-\frac{1}{(-2 R)}\right) \)