Manipal Medical Manipal Medical Solved Paper-2013

  • question_answer
    When electron is accelerated between 500 keV, what is the percentage increase in mass?

    A)  82.35%             

    B)  97.85%

    C)  42.35%             

    D)  59.45%

    Correct Answer: B

    Solution :

     Kinetic energy of photoelectron \[KE=500\,keV=500\times {{10}^{3}}eV\] \[KE=m{{c}^{2}}-{{m}_{0}}{{c}^{2}}\] \[\frac{KE}{{{m}_{0}}{{c}^{2}}}=\frac{m{{c}^{2}}-{{m}_{0}}{{c}^{2}}}{{{m}_{0}}}\] \[=\frac{m-{{m}_{0}}}{{{m}_{0}}}=\frac{\Delta m}{{{m}_{0}}}\] \[\frac{\Delta m}{m}=\frac{KE}{{{m}_{0}}{{c}^{2}}}\] Hence % increase in mass is \[=\frac{\Delta m}{m}\times 100=\frac{KE}{{{m}_{0}}{{c}^{2}}}\times 100\] \[=\frac{500\times {{10}^{3}}}{0.511\times {{10}^{6}}}\times 100\] \[=\frac{5}{5.11}\times 100=97.85%\]


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