Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2006

  • question_answer
    If the frequency of \[{{K}_{a,}}\] .X-ray of the element of atomic number 31 is/, then the frequency of\[{{K}_{a,}}\] X-ray for atomic number 51 is

    A) \[\text{25/9}f\]                               

    B)  \[\text{16/25}f\]

    C)  \[\text{9/25}f\]                              

    D)  zero

    Correct Answer: A

    Solution :

    Wavelength of \[{{K}_{\alpha }},\] X-ray \[\lambda \propto \frac{1}{{{(Z-1)}^{2}}}\]                 \[\therefore \]  \[\frac{{{\lambda }_{2}}}{{{\lambda }_{1}}}=\frac{{{({{Z}_{1}}-1)}^{2}}}{{{({{Z}_{2}}-1)}^{2}}}\] But,         \[\lambda \propto \frac{1}{frequency\,(f)}\] \[\therefore \]  \[\frac{{{f}_{1}}}{{{f}_{2}}}=\frac{{{({{Z}_{1}}-1)}^{2}}}{{{({{Z}_{2}}-1)}^{2}}}\] or            \[\frac{f}{{{f}_{2}}}=\frac{{{(31-1)}^{2}}}{{{(51-1)}^{2}}}=\frac{900}{2500}\] \[\therefore \]  \[{{f}_{2}}=\frac{25}{9}f\]


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