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Most Important Selected Qs for JEE AdvancedPhysicsRay Optics

Position of object O and screen is fixed and lens is moved. At two positions of lens we get clear image on the screen. First position is at 30 cm from object and second position is at 50 cm from object. Find focal length of lens (in cm)

Options

  1. A25 4
  2. B75 4
  3. C45 4
  4. D65 4

Correct answer

B. 75 4

Step-by-step solution

V and U will get interchange on changing object position. aligned & 1 f = 1 30 + 1 50 & f= 1500 80 = 75 4 ~cm aligned

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