MGIMS WARDHA MGIMS WARDHA Solved Paper-2015

  • question_answer
    \[{{\lambda }_{1}},{{\lambda }_{2}}\]and\[{{\lambda }_{3}}\]are de-Broglie wavelengths of electron, proton and\[\alpha -\]particle. If they are accelerated by same potential, then

    A)  \[{{\lambda }_{1}}<{{\lambda }_{2}}<{{\lambda }_{3}}\]                              

    B)  \[{{\lambda }_{1}}>{{\lambda }_{2}}>{{\lambda }_{3}}\]

    C)  \[{{\lambda }_{1}}<{{\lambda }_{2}}>{{\lambda }_{3}}\]                              

    D)  \[{{\lambda }_{1}}>{{\lambda }_{2}}<{{\lambda }_{3}}\]

    Correct Answer: B

    Solution :

                    The de-Broglie wavelength is given as \[\lambda =\frac{h}{\sqrt{2mqV}}\] Here, h and V are constants so,          \[\lambda \propto \frac{1}{\sqrt{mq}}\] \[\therefore \]\[{{\lambda }_{1}}:{{\lambda }_{2}}:{{\lambda }_{3}}=\frac{1}{\sqrt{{{m}_{1}}{{q}_{1}}}}:\frac{1}{\sqrt{{{m}_{2}}{{q}_{2}}}}:\frac{1}{\sqrt{{{m}_{3}}{{q}_{3}}}}\] \[=\frac{1}{\sqrt{\frac{{{m}_{p}}}{1840}\times e}}:\frac{1}{\sqrt{{{m}_{p}}\times e}}:\frac{1}{\sqrt{4{{m}_{p}}\times 2e}}\]                 \[=\sqrt{1840}:1:\frac{1}{2\sqrt{2}}\] So          \[{{\lambda }_{1}}>{{\lambda }_{2}}>{{\lambda }_{3}}\]


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