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JEE Main & Advanced Physics Ray Optics Question Bank Critical Thinking

  • question_answer
    A point object is moving on the principal axis of a concave mirror of focal length \[24cm\] towards the mirror. When it is at a distance of \[60cm\] from the mirror, its velocity is \[9cm/sec.\] What is the velocity of the image at that instant [MP PMT 1997]

    A)            \[5cm/sec\] towards the mirror

    B)            \[4cm/sec\] towards the mirror

    C)            \[4cm/sec\] away from the mirror

    D)            \[9cm/\sec \] away from the mirror

    Correct Answer: C

    Solution :

               \[{{v}_{i}}=-{{\left( \frac{f}{f-u} \right)}^{2}}.\,{{v}_{o}}\]\[=-\,{{\left( \frac{-24}{-24-(-60)} \right)}^{2}}\times 9\]= 4 cm/sec.


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