J & K CET Engineering J and K - CET Engineering Solved Paper-2004

  • question_answer
    An electron and a proton are accelerated through the same potential difference. The ratio of their de-Broglie wavelength will be

    A)  \[{{\left( \frac{{{m}_{p}}}{{{m}_{e}}} \right)}^{1/2}}\]

    B)  \[\frac{{{m}_{e}}}{{{m}_{p}}}\]

    C)  \[\frac{{{m}_{p}}}{{{m}_{e}}}\]

    D)  \[\frac{a}{\sqrt{2}}\]

    Correct Answer: A

    Solution :

    de-Broglie wavelength \[(\lambda )\] is given by \[\lambda =\frac{h}{p}\] where h is Planck's constant, and p the momentum. Also,   \[p=\sqrt{2mE}=\sqrt{2mqV}\] where E is energy, q the charge and V the potential difference. \[\therefore \] \[\lambda =\frac{h}{\sqrt{2mqV}}\] Hence, the ratio of wavelength of electron \[({{\lambda }_{e}})\]and proton \[({{\lambda }_{p}})\] is \[\frac{{{\lambda }_{e}}}{{{\lambda }_{p}}}=\sqrt{\frac{{{m}_{p}}}{{{m}_{e}}}}={{\left( \frac{{{m}_{p}}}{{{m}_{e}}} \right)}^{1/2}}\]


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