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Ray Optics and Optical Instruments · Class 12 · CBSE · Science Physics

A point object is placed at a distance of 30 cm from a convex mirror of focal length 30 cm. The image is formed at:

Practice question from Ray Optics and Optical Instruments (Class 12 · CBSE · Science Physics), with the correct answer and a step-by-step solution.

easy · MCQ · Q-6D8744

A point object is placed at a distance of 30 cm from a convex mirror of focal length 30 cm. The image is formed at:

  1. A.Infinity
  2. B.15 cm behind the mirrorCorrect answer
  3. C.15 cm in front of the mirror
  4. D.30 cm behind the mirror

Solution

Using the mirror formula, 1/f=1/v+1/u1/f = 1/v + 1/u. Given f=+30 cmf = +30\text{ cm} and u=−30 cmu = -30\text{ cm}, we get 1/30=1/v−1/(−30)1/30 = 1/v - 1/(-30), which gives 1/v=1/30−1/30=01/v = 1/30 - 1/30 = 0, so v=+15 cmv = +15\text{ cm}. Thus, the image is formed 15 cm behind the mirror.

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