NEET Sample Paper NEET Sample Test Paper-68

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

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

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

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

    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. \[{{P}_{H}}-atom={{P}_{photon}}\,=\,\,\frac{{{E}_{radicated}}}{c}\] \[=\,\,\frac{13.6\left( \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right)eV}{c}\] \[1.6\,\,\times \,\,{{10}^{-27}}\,\times \,\,\nu \,\,=\,\,\frac{13.6\left( \frac{1}{{{1}^{2}}}-\frac{1}{{{5}^{2}}} \right)\,\,1.6\times {{10}^{-19}}}{3\times {{10}^{8}}}\] \[\Rightarrow \,\,\,\nu  =4.352\,m/s \approx  4 m/s.\]


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