CMC Medical CMC-Medical Ludhiana Solved Paper-2014

  • question_answer
    If uncertainties in the measurement of position and momentum of an electron are equal, the uncertainty in the measurement of velocity is

    A)  \[8.0\times {{10}^{12}}m{{s}^{-1}}\]      

    B)  \[4.2\times {{10}^{10}}m{{s}^{-1}}\]

    C)  \[8.5\times {{10}^{10}}m{{s}^{-1}}\]      

    D)  \[6.2\times {{10}^{10}}m{{s}^{-1}}\]

    Correct Answer: A

    Solution :

                    Given, \[\Delta \,x=\Delta P\]or \[\Delta \,x=m\cdot \Delta v\] From Heisenbergs uncertainty principle, \[\Delta \,x\cdot m\cdot \Delta v=\frac{h}{4\pi }\] \[\Rightarrow \]               \[m\cdot \Delta v\cdot m\Delta v=\frac{h}{4\pi }\]                                 \[{{(\Delta v)}^{2}}=\frac{h}{4\pi {{m}^{2}}}\] \[\Rightarrow \]                               \[\Delta v=\frac{1}{2m}\sqrt{\frac{h}{\pi }}\]                                 \[=\frac{1}{2\times 9.1\times {{10}^{-31}}}\sqrt{\frac{6.63\times {{10}^{-34}}}{3.14}}\]                                 \[=7.98\times {{10}^{12}}m{{s}^{-1}}\]                                 \[=8\times {{10}^{12}}m{{s}^{-1}}\]


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