NEET Chemistry Structure of Atom / परमाणु संरचना NEET PYQ-Structure of Atom

  • question_answer
    Given:   The mass of electron is \[9.11\times {{10}^{-31}}kg\] Planck constant is \[6.626\times {{10}^{-34}}Js\], the uncertainty involved in the measurement of velocity within a distance of \[0.1\,\,\overset{o}{\mathop{A}}\,\] is :                                                                                                                                               [AIPMT (S) 2006]

    A) \[5.79\times {{10}^{6}}m{{s}^{-1}}\]

    B)  \[5.79\times {{10}^{{}}}m{{s}^{-1}}\]

    C)  \[5.79\times {{10}^{8}}m{{s}^{-1}}\]

    D)       \[5.79\times {{10}^{5}}m{{s}^{-1}}\]

    Correct Answer: A

    Solution :

               
    By Heisenberg's uncertainty principle
    \[\Delta p\times \Delta x\ge \frac{h}{4\pi }\]
    or         \[\Delta v\times \Delta x\ge \frac{h}{4\pi m}\]
    \[\Delta p\to \,\] uncertainty in momentum
    \[\Delta x\to \,\] uncertainty in position
    \[\Delta v\to \,\] uncertainty in velocity
    \[m\to \,\] mass of particle
    Given that,
    \[\Delta x=0.1\,{\AA}=0.1\times {{10}^{-10}}\,m\]
    \[\Delta x=0.1\,{\AA}=0.1\times {{10}^{-10}}\,m\]
    \[m=9.11\times {{10}^{-31}}\,kg\]
    \[h=Planck\,\text{constant}\,=6.626\times {{10}^{-34}}\,Js\]
    \[\pi =3.14\]
    In uncertain position \[\Delta v\times \Delta x=\frac{h}{4\pi m}\]
    \[\Delta v\times 0.1\times {{10}^{-10}}=\frac{6.626\times {{10}^{-34}}}{4\times 3.14\times 9.11\times {{10}^{-31}}}\]
    \[\Delta v=\frac{6.626\times {{10}^{-34}}}{4\times 3.14\times 9.11\times {{10}^{-31}}\times 0.1\times {{10}^{-10}}}\,m{{s}^{-1}}\]
    \[=5.785\times {{10}^{6}}\,m{{s}^{-1}}\]
    \[=5.79\times {{10}^{6}}\,m{{s}^{-1}}\]


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