JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Morning)

  • question_answer
    A hydrogen atom, initially in the ground state, is excited by absorbing a photon of wavelength\[980\overset{o}{\mathop{A}}\,\]. The radius of the atom in the excited state, in terms of Bohr radius \[{{a}_{0}},\]will be \[(hc\,=12500\,eV-\overset{o}{\mathop{A}}\,)\] [JEE Main Online Paper (Held On 11-Jan-2019 Morning]

    A) \[9{{a}_{0}}\]              

    B)     \[16{{a}_{0}}\]

    C) \[4{{a}_{0}}\]              

    D)                  \[25{{a}_{0}}\]

    Correct Answer: B

    Solution :

    The energy absorbed by the atom is\[\frac{hc}{\lambda }\] So,\[\frac{hc}{\lambda }=-13.6\left( \frac{1}{n_{2}^{2}}-\frac{1}{n_{1}^{2}} \right)\] \[\Rightarrow \]\[\frac{12500}{980\times 13.6}=\frac{1}{{{(1)}^{2}}}-\frac{1}{n_{2}^{2}}\Rightarrow {{n}_{2}}\simeq 4\] The radius of \[{{n}^{th}}\] orbit is \[{{a}_{0}}{{n}^{2}}.\] So, the radius of atom in excited state is \[{{4}^{2}}{{a}_{0}}=16{{a}_{0}}\]


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