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BITSAT2013PhysicsRay OpticsActual

The given lens is broken into four parts and rearranged as shown. If the initial focal length is f then after rearrangement the equivalent focal length is-

Options

  1. Af
  2. Bf / 2
  3. Cf / 4
  4. D4 f

Correct answer

B. f / 2

Step-by-step solution

Cutting a lens in transverse direction doubles their focal length i.e. 2 f . Using the formula of equivalent focal length, 1 f = 1 f₁ + 1 f₂ + 1 f₃ + 1 f₄ We get equivalent focal length as f / 2

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