AMU Medical AMU Solved Paper-2012

  • question_answer
    The de-Broglie wavelength of an electron moving with a velocity \[1.5\times {{10}^{8}}m/s\]is equal to that of a photon. The ratio of the kinetic energy of the electron to the energy of the photon is

    A)  \[\frac{1}{4}\]                                  

    B)  \[\frac{1}{2}\]

    C)  2                                            

    D)  4

    Correct Answer: A

    Solution :

                    \[{{K}_{e}}=\frac{1}{2}m{{v}^{2}}\] and \[\lambda =\frac{h}{mv}\]                 \[{{K}_{e}}=\frac{1}{2}\left( \frac{h}{\lambda v} \right)\,.\,{{v}^{2}}=\frac{vh}{2\lambda }\]                 \[{{K}_{p}}=\frac{hc}{\lambda }\] \[\therefore \]  \[\frac{{{K}_{e}}}{{{K}_{p}}}=\frac{v}{2\,c}\]                 \[=\frac{1.5\times {{10}^{8}}}{2\times 3\times {{10}^{8}}}=\frac{1}{4}\]


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