JCECE Medical JCECE Medical 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\[\text{o }\!\!|\!\!\text{ }\]because it is normally so small compared to\[\text{e}{{\text{V}}_{0}}\]). \[\therefore \] \[e{{V}_{0}}=h{{v}_{\max }}\] or \[e{{V}_{0}}=\frac{hc}{{{\lambda }_{\min }}}\] \[\therefore \] \[{{V}_{0}}=\frac{hc}{e{{\lambda }_{\min }}}\] or \[{{V}_{0}}=\frac{12400\times {{10}^{-10}}}{{{10}^{-11}}}\] \[=124\,kV\] 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