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BVP Medical BVP Medical Solved Paper-2003

  • question_answer
    The distance at which an object should be placed in front of a convex lens focaI length 10 cm to obtain a real image double the size of object will be :

    A)  30 cm                                  

    B)  15 cm

    C)  5 cm                                     

    D)  10 cm

    Correct Answer: B

    Solution :

                    Given \[m=\frac{\upsilon }{u}=2\] or  \[\upsilon =2u\] For real image, u is negative and \[\upsilon \] is positive, from formula                 \[\frac{1}{f}=\frac{1}{\upsilon }-\frac{1}{u}\] or            \[\frac{1}{f}=\frac{1}{\upsilon }-\frac{1}{-\upsilon }=\frac{1}{\upsilon }+\frac{1}{u}\] or            \[\frac{1}{10}=\frac{1}{2u}+\frac{1}{u}=\frac{3}{2u}\] Hence,   \[u=\frac{30}{2}=15cm\]


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