JEE Main & Advanced Sample Paper JEE Main - Mock Test - 19

  • question_answer
    If in hydrogen atom, radius of \[{{n}^{th}}\] Bohr orbit is \[{{r}_{n}},\] frequency of revolution of electron in  \[{{n}^{th}}\]orbit is \[{{f}_{n}},\] choose the correct option.

    A)  

    B)       

    C)

    D) Both (a) and (b)

    Correct Answer: D

    Solution :

    Radius of \[{{n}^{th}}\] orbit \[{{r}_{n}}\propto {{n}^{2}},\] graph between \[{{r}_{n}}\] and n is a parabola. Also, \[\frac{{{r}_{n}}}{{{r}_{1}}}={{\left( \frac{n}{1} \right)}^{2}}\Rightarrow {{\log }_{e}}\left( \frac{{{r}_{n}}}{{{r}_{1}}} \right)=2{{\log }_{e}}(n)\] Comparing this equation with \[y=mx+c,\] Graph between \[{{\log }_{e}}\left( \frac{{{r}_{n}}}{{{r}_{1}}} \right)\] and \[{{\log }_{e}}(n)\] will be a straight line, passing from origin. Similarly it can be proved that graph between \[{{\log }_{e}}\left( \frac{{{f}_{n}}}{{{f}_{1}}} \right)\] and \[{{\log }_{e}}n\]is a straight line. But with negative slops.


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