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A linear object is placed along the axis of a mirror as shown in the figure. If f is the focal length of the mirror, then the length of the image is

Options

  1. A2 f 3
  2. Bf
  3. Cf 3
  4. Dnone

Correct answer

B. f

Step-by-step solution

The image of object at 2 f will be formed at 2 f . So the object and image will coincide at 2 f . 1 v - 1 u = 1 f 1 v - 1 - 3 f 2 = 1 f 1 v = 1 f - 2 3 f = 1 3 f ∴ Length of image = 3 f - 2 f = f

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