BHU PMT BHU PMT Solved Paper-2001

  • question_answer
    The energy of hydrogen atom in the nth orbit is\[{{E}_{n}},\]Then the energy in the nth orbit of single Ionized helium atom is:

    A)  \[\frac{{{E}_{n}}}{2}\]                                  

    B)  \[2{{E}_{n}}\]

    C)  \[4{{E}_{n}}\]                   

    D)  \[\frac{{{E}_{n}}}{4}\]

    Correct Answer: C

    Solution :

    The energy of election of charge \[e\], mass \[m\], in an orbit is the sum of kinetic and potential energies. The total energy in the \[nth\] orbit is given by \[E=-\frac{m{{Z}^{2}}{{e}^{4}}}{8\varepsilon _{0}^{2}{{h}^{2}}}\left( \frac{1}{{{n}^{2}}} \right)\] Where Z is atomic number. For helium \[Z=2\] \[\therefore \]  \[E\propto {{Z}^{2}}\propto {{\left( 2 \right)}^{2}}\propto 4\] \[\Rightarrow \]                               \[E=4\,{{E}_{n}}\]           


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