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A double convex lens has focal length 25 ~cm . The radius of curvature of one of the surfaces is doubled of the other. Find the radii, if the refractive index of the material of the lens is 1.5.

Options

  1. A100 ~cm , 50 ~cm
  2. B25 ~cm , 50 ~cm
  3. C18.75 ~cm , 37.5 ~cm
  4. D50 ~cm , 100 ~cm

Correct answer

C. 18.75 ~cm , 37.5 ~cm

Step-by-step solution

( aligned & 1 f =( -1) [ 1 R ₁ - 1 R ₂ ] & 1 25 =0.5 [ 1 R - ( 1 2 R ) ] & 1 25 = 0.5 10 [ 3 R ] & R = 75 4 =18.75 & R ₁=18.75 ~cm , R ₂=37.5 ~cm aligned )

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