RAJASTHAN ­ PET Rajasthan PET Solved Paper-2012

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

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

    B)  \[5.79\times {{10}^{7}}m{{s}^{-1}}\]

    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         \[\Delta v\times \Delta x\ge \frac{h}{4\pi m}\] \[\Delta x=\]uncertainty in position \[0.1\overset{o}{\mathop{\text{A}}}\,=0.1\times {{10}^{-10}}m\] \[m=\]mass of particle \[9.11\times {{10}^{-31}}kg\] \[h=\]Planck constant\[=6.626\times {{10}^{-34}}Js\] \[\pi =3.14\] \[\Delta v=\]uncertainty in velocity = ? 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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