JEE Main & Advanced Physics Atomic Physics JEE PYQ-Atomic Physics

  • question_answer
    Muon \[\left( {{\mu }^{-1}} \right)\] is negatively charged \[(|q|=|e|)\]with a mass \[{{m}_{\mu }}=200{{m}_{e}},\] where \[{{m}_{e}}\] is the mass of the electron and \[e\] is the electronic charge. If \[{{\mu }^{-1}}\] is bound to a proton to form a hydrogen like atom, identify the correct statements             [JEE Online 15-04-2018 (II)]
    [A] Radius of the muonic orbit is times smaller than that of the electron
    [B] the speed of the \[{{\mu }^{-1}}\] in the nth orbit is\[\frac{1}{200}\] times that of the electron in the nth orbit
    [C] The ionization energy of muonic atom is 200 times more than that of an hydrogen atom
    [D] The momentum of the muon in the nth orbit is 200 times more than that of the electron

    A) , ,

    B) ,

    C) ,

    D) , ,

    Correct Answer: A

    Solution :

    [a] [a] Radius of muon
    \[\text{=}\frac{\text{Radius of hydrogen}}{200}\]
    \[\text{Radius of H atom=r=}\frac{{{\in }_{o}}{{n}^{2}}{{h}^{2}}}{\pi m{{e}^{2}}}\]
    \[\text{Radius of muon =}{{\text{r}}_{\mu }}=\frac{{{\in }_{o}}{{n}^{2}}{{h}^{2}}}{\pi \times 200m{{e}^{2}}}\]
    \[{{r}_{\mu }}=\frac{r}{200}\]
    [b] Velocity relation given is wrong
    [c] Ionization energy in \[{{e}^{-}}H\] atom
    \[E=\frac{+m{{e}^{4}}}{8\in -{{o}^{2}}{{n}^{2}}{{h}^{2}}}\]
    \[{{E}_{\mu }}=\frac{200m{{e}^{4}}}{8\in _{o}^{2}{{n}^{2}}{{h}^{2}}}=200E\]
    [d] Momentum of H-atom
    \[mvr=\frac{nh}{2\pi }\]
    momentum of muon is \[200\times mvr\]
    hence , [c] & [d] are correct


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