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NEET2012PhysicsRay OpticsActual

The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 ~cm . The focal length of lenses are

Options

  1. A10 ~cm , 10 ~cm
  2. B15 ~cm , 5 ~cm
  3. C18 ~cm , 2 ~cm
  4. D11 ~cm , 9 ~cm

Correct answer

C. 18 ~cm , 2 ~cm

Step-by-step solution

Given, M= f₀ f_e =9 and f₀+f_e=20f_o=9 f_e So, 9 f_e+f_e=20 aligned & f_e=2 ~cm & f_o=9 2 & f₀=18 ~cm aligned

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