CET Karnataka Medical CET - Karnataka Medical Solved Paper-2012

  • question_answer
    A proton and an alpha particle are accelerated under the same potential difference. The ratio of de-Broglie wavelengths of the proton and the alpha particle is

    A)  \[\sqrt{8}\]    

    B)  \[\frac{1}{\sqrt{8}}\]   

    C)  \[1\]     

    D)  \[2\]

    Correct Answer: A

    Solution :

    : When a charged particle of charge q and mass m is accelerated under a potential difference V, let \[\upsilon \] be velocity acquired by the particle. Then \[qV=\frac{1}{2}m{{\upsilon }^{2}}\] or  \[m\upsilon =\sqrt{2mqV}\] de Broslie wavelength, \[\lambda =\frac{h}{m\upsilon }=\frac{h}{\sqrt{2mqV}}\] \[\lambda \propto \frac{1}{\sqrt{mq}}\] for the same value of V. \[\therefore \] \[\frac{{{\lambda }_{p}}}{{{\lambda }_{\alpha }}}=\frac{\sqrt{{{m}_{\alpha }}{{q}_{\alpha }}}}{\sqrt{{{m}_{p}}{{q}_{p}}}}=\sqrt{\frac{4m}{m}\times \frac{2e}{e}}=\sqrt{8}\]


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