JEE Main & Advanced Physics Ray Optics Sample Paper Topic Test - Refraction of Light Through Curved Surfaces

  • question_answer
    When an object is at distances x and y from a lens, a real image and a virtual image is formed respectively having same magnification. The focal length of the lens is:

    A) \[\frac{x+y}{2}\]

    B) \[x-y\]

    C) \[\sqrt{xy}\]

    D) \[x+y\]

    Correct Answer: A

    Solution :

    [a] The given lens is convex lens. Let the magnification be m, then for real image
    \[\frac{1}{mx}+\frac{1}{x}=\frac{1}{f}\] ...(i)
    and for virtual image
    \[\frac{1}{-my}+\frac{1}{y}=\frac{1}{f}\] ...(ii)
    From Eq. (i) and Eq. (ii) .we get \[f=\frac{x+y}{2}\]

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