JEE Main & Advanced Sample Paper JEE Main Sample Paper-21

  • question_answer
    Electron with de-Broglie wavelength \[\lambda \] fall on the target in an \[X-\]ray tube. The cut-off wavelength of the emitted \[X-\] rays is :

    A)  \[{{\lambda }_{0}}=\frac{2mc{{\lambda }^{2}}}{h}\]            

    B)  \[{{\lambda }_{0}}=\frac{2h}{m}\]

    C)  \[{{\lambda }_{0}}=\frac{2{{m}^{2}}-{{c}^{2}}{{\lambda }^{3}}}{{{h}^{2}}}\]

    D)  \[{{\lambda }_{0}}=\lambda \]

    Correct Answer: A

    Solution :

    \[P=h/\lambda \] And \[K=\frac{{{P}^{2}}}{2m}\,=\frac{{{h}^{2}}}{2m{{\lambda }^{2}}}\] For X-ray photons, it is also maximum energy So, \[\frac{hc}{{{\lambda }_{0}}}\,=\frac{{{h}^{2}}}{2m{{\lambda }^{2}}}\]Or, \[{{\lambda }_{0}}\,=\frac{2m{{\lambda }^{2}}c}{h}\,\]


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