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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 :

Options

  1. A2 R
  2. BR 2
  3. C3 R 2
  4. DR 3

Correct answer

D. R 3

Step-by-step solution

1 P = ( n - 1 ) 1 R - 1 - R 1 P = ( n - 1 ) 2 R ......... 1 1 1 . 5 P = ( n - 1 ) 1 R - 1 ∞ ....... ii 2 3 P = n - 1 R From i and ii 3 2 = R ' 2 R ⇒ R ' = R 3

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