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JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank Critical Thinking

  • question_answer
    The wavelength Ka X-rays produced by an X-ray tube is 0.76 Å. The atomic number of anticathode material is

    A)            82  

    B)            41

    C)            20  

    D)            10

    Correct Answer: B

    Solution :

                For \[{{K}_{\alpha }}\] X-ray line                    \[\frac{1}{{{\lambda }_{\alpha }}}=R{{(Z-1)}^{2}}\left[ \frac{1}{{{1}^{2}}}-\frac{1}{{{2}^{2}}} \right]=\frac{3R}{4}{{(Z-1)}^{2}}\]                    On putting the given values                    \[\frac{1}{0.76\times {{10}^{-10}}}=\frac{3}{4}\times 1.09\times {{10}^{7}}{{(Z-1)}^{2}}\]                    Þ \[{{(Z-1)}^{2}}\approx 1600\] Þ \[Z-1=40\] Þ \[Z=41\]


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