JEE Main & Advanced Sample Paper JEE Main Sample Paper-11

  • question_answer
    If \[{{E}_{1}},{{E}_{2}},\] and \[{{E}_{3}}\]represent respectively the kinetic energies of an electron and an alpha particle and a proton each having same de-broglie wavelength then

    A)  \[{{E}_{1}}>{{E}_{3}}>{{E}_{2}}\]                             

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

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

    D)  \[{{E}_{1}}={{E}_{2}}={{E}_{3}}\]

    Correct Answer: A

    Solution :

     Since K.E. \[\frac{1}{2}m{{v}^{2}}\]and \[\lambda =\frac{h}{mv}.\] \[\therefore \]  \[K.E.=\frac{1}{2}m.\frac{{{h}^{2}}}{{{m}^{2}}{{\lambda }^{2}}}=\frac{{{h}^{2}}}{2m{{\lambda }^{2}}}.\]As \[\lambda \]is the same. \[\therefore \]  \[K.E.\propto \frac{1}{m}\]


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