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MHT CET202311 May 2023Evening ShiftPhysicsRay OpticsActual

A double convex lens of focal length ' F ' is cut into two equal parts along the vertical axis. The focal length of each part will be

Options

  1. A2 ~F
  2. BF
  3. CF 2
  4. D4 ~F

Correct answer

A. 2 ~F

Step-by-step solution

For bifocal convex lens 1 f =( -1) ( 1 R₁ + 1 R₂ )= ( -1) 2 R . (R₁=R₂=R ) For plane surface R ₂= For half plane-convex lens aligned & 1 f ^ =( -1) 1 R & 1 / f 1 / f ^ = ( -1) R 2 R -1 =2 & f ^ f =2 & f ^ =2 f aligned As focal length is F, f^ =2 F .

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