Haryana PMT Haryana PMT Solved Paper-2010

  • question_answer
    A hydrogen atom emits a photon corresponding to an electron transition from n = 5 to n = 1. The recoil speed of hydrogen atom is almost (mass   of proton \[\approx 1.6\times {{10}^{-27}}kg)\]

    A)  \[10m{{s}^{-1}}\]                           

    B)  \[2\times {{10}^{-2}}m{{s}^{-1}}\]

    C)  \[4m{{s}^{-1}}\]                              

    D)  \[8\times {{10}^{2}}m{{s}^{-1}}\]

    Correct Answer: C

    Solution :

                    The hydrogen atom before the transition was at rest.   Therefore,   from  conservation   of momentum \[{{P}_{H-atom}}={{P}_{photon}}=\frac{{{E}_{radiated}}}{c}=\frac{13.6\left[ \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right]eV}{c}\] \[1.6\times {{10}^{-27}}\times v=\frac{13.6\left[ \frac{1}{{{1}^{2}}}-\frac{1}{{{5}^{2}}} \right]\times 1.6\times {{10}^{-19}}}{3\times {{10}^{6}}}\] \[\Rightarrow \]               \[v=4.352m/s=\,\,\approx 4m/s\]


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