CMC Medical CMC-Medical Ludhiana Solved Paper-2015

  • question_answer
    An H-atom is initially in ground, state absorbs a photon, which excites it upto n = 4 level. The wavelength of emitted radiation is

    A)  97 nm                                  

    B)  82 nm

    C)  67 nm                  

    D)  107 nm

    Correct Answer: A

    Solution :

                    As, \[E=\frac{-13.6}{{{n}^{2}}}eV\] For \[n=1,\,\,{{E}_{1}}=\frac{-13.6}{{{1}^{2}}}eV=-13.6\,eV\] For \[n=4,\,\,{{E}_{2}}=\frac{-13.6}{{{4}^{2}}}eV=-0.85\,eV\] Now, \[\Delta E={{E}_{2}}-{{E}_{1}}=-0.85-(-13.6)\] \[=12.75\,eV\] \[=2.04\times {{10}^{-18}}J\] This energy is equivalent to energy of photon i.e. \[2.04\times {{10}^{-18}}=\frac{hc}{\lambda }\] \[\Rightarrow \]               \[\lambda =\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{2.04\times {{10}^{-18}}}=97\,nm\]


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