NEET Sample Paper NEET Sample Test Paper-65

  • question_answer
    If a voltage applied to an X-ray tube is increased to 1.5 times the minimum wavelength \[({{\lambda }_{min}})\] of an X-ray continuous spectrum shifts by\[\Delta \,\lambda  = 26 pm\]. The initial voltage applied to the tube is

    A) \[\approx \,\,10\text{ }kV\]

    B)               \[\approx \,\,16\text{ }kV\]

    C) \[\approx \,\,50\text{ }kV\]                     

    D) \[\approx \,\,75\text{ }kV\]

    Correct Answer: B

    Solution :

    \[{{\lambda }_{min}}\,=\,\,\frac{hc}{eV}\,\,\,\,\Rightarrow \,\,{{\lambda }_{1}}\,=\,\,\frac{hc}{e{{V}_{1}}}\,\,and\,\,{{\lambda }_{2}}\,=\,\,\frac{hc}{e{{V}_{2}}}\] \[\therefore \,\,\Delta \lambda ={{\lambda }_{2}}-{{\lambda }_{1}}\,=\,\,\frac{hc}{e}\left[ \frac{1}{{{V}_{2}}}-\frac{1}{{{V}_{1}}} \right]\] \[Given\,\,{{V}_{2}}=1.5\,{{V}_{1}}\] On solving, we get \[{{\operatorname{V}}_{1}} =16000 volt = 16 kV.\]


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