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NEET Sample Paper NEET Sample Test Paper-43

  • question_answer
    When an object is at distance 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 :

    The given lens is a 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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