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    Question

    The focal length of a concave mirror is 20 cm. Where

    should an object be placed to get an image of the same size?
    A 10 cm Correct Answer Incorrect Answer
    B 20 cm Correct Answer Incorrect Answer
    C 40 cm Correct Answer Incorrect Answer
    D At infinity Correct Answer Incorrect Answer

    Solution

    For a concave mirror, an image equal in size and real is formed when the object is placed at the center of curvature. The center of curvature is at a distance 2f = 40 cm, so half that is 20 cm from the mirror. At this position, image is real, inverted, and same size. Hence, the correct position is at 20 cm.

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