JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    If \[10000\,\,V\] is applied across an X-ray tube, what will be the ratio of de-Broglie wavelength of the incident electrons to the shortest wavelength X-ray produced?                 \[\left( \frac{e}{m}\,\,for\,\,electron=1.8\times {{10}^{11}}C\,\,k{{g}^{-1}} \right)\]

    A) \[0.1\]                                  

    B) \[0.2\]

    C)  \[0.3\]                                 

    D)  \[1.0\]

    Correct Answer: A

    Solution :

    For incident electron,\[\frac{1}{2}m{{v}^{2}}=eV\] or            \[{{p}^{2}}=2meV\] \[\therefore \]de-Broglie wavelength,\[{{\lambda }_{1}}=\frac{h}{p}=\frac{h}{\sqrt{2meV}}\] Shortest X-rays wavelength,\[{{\lambda }_{2}}=\frac{hc}{eV}\] \[\therefore \]  \[\frac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\frac{1}{c}\sqrt{\left( \frac{V}{2} \right)\left( \frac{e}{m} \right)}\]                 \[=\frac{\sqrt{\frac{{{10}^{4}}}{2}\times 1.8\times {{10}^{11}}}}{3\times {{10}^{8}}}=0.1\]


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