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A convex lens of focal length 20 c m produces images of the same magnification 2 when an object is kept at two distances x 1 and x 2 x 1 > x 2 from the lens. The ratio of x 1 and x 2 is:

Options

  1. A2 : 1
  2. B5 : 3
  3. C4 : 3
  4. D3 : 1

Correct answer

D. 3 : 1

Step-by-step solution

Given, m = 2 ⇒ m = ± 2 From this lens formula, 1 v + 1 u = 1 f u v + 1 = u f 1 m + 1 = u f u = f 1 m + 1 x 1 = 20 1 + 1 2 x 2 = 20 1 - 1 2 x 1 x 2 = 3 1

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