JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    Hard \[X-\]rays for the study of fractures in bones should have a minimum wavelength of\[{{10}^{-11}}m\]. The accelerating voltage for electrons in X-ray machine should be

    A)  \[<124\,\,kV\]

    B)  \[>124\,\,kV\]

    C)  between\[60\,\,kV\]and\[70\,\,kV\]

    D)   \[=100\,\,kV\]

    Correct Answer: A

    Solution :

    From conservation of energy the kinetic energy of electron equals the maximum photon energy (we neglect the work function \[\phi \] because it is normally so small compared to \[e{{V}_{0}})\]. \[\therefore \]  \[e{{V}_{0}}=h{{v}_{\max }}\] or            \[e{{V}_{0}}=\frac{hc}{{{\lambda }_{\min }}}\] \[\therefore \]  \[{{V}_{0}}=\frac{hc}{e{{\lambda }_{\min }}}\] or            \[{{V}_{0}}=\frac{12400\times {{10}^{-10}}}{{{10}^{-11}}}\] Hence, accelerating voltage for electrons in \[X-\]ray machine should be less than\[124\,\,kV\].


You need to login to perform this action.
You will be redirected in 3 sec spinner