JEE Main & Advanced Sample Paper JEE Main - Mock Test - 29

  • question_answer
    In a hydrogen atom, an electron jumps from the state n to n -1 where \[n>>1\]. The frequency of the emitted radiation is proportional to

    A) \[{{n}^{0}}\]              

    B) \[{{n}^{-1}}\]

    C) \[{{n}^{-2}}\]             

    D) \[{{n}^{-3}}\]

    Correct Answer: D

    Solution :

    [d]: According to Bohr?s theory of hydrogen atom \[\frac{1}{\lambda }=R{{Z}^{2}}\left( \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right)\] \[\upsilon =\frac{c}{\lambda }=Rc{{Z}^{2}}\left( \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right)\] \[\therefore \]\[\upsilon \propto \left( \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right)=\frac{n_{2}^{2}-n_{1}^{2}}{n_{1}^{2}n_{2}^{2}}\] \[\upsilon \propto \left( \frac{{{n}^{2}}-{{(n-1)}^{2}}}{{{n}^{2}}{{(n-1)}^{2}}} \right)=\frac{2n-1}{{{n}^{2}}{{(n-1)}^{2}}}\] When \[n>>1,\] \[\upsilon \propto \frac{2n}{{{n}^{4}}},\]i.e.,\[\upsilon \propto \frac{1}{{{n}^{3}}}\]or\[\upsilon \propto {{n}^{-3}}\]


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