RAJASTHAN ­ PET Rajasthan PET Solved Paper-2007

  • question_answer
    To look inside an atom of diameter 100 pm we have to penetrate it upto a breadth of 10 pm. If we use an electron microscope, the minimum required energy will be

    A)  1.5 keV          

    B)  15 keV

    C)  150 keV         

    D)  1.05 keV

    Correct Answer: B

    Solution :

     The de-Broglie wavelength \[\lambda =\frac{h}{p}=\frac{h}{mv}\] Or \[v=\frac{h}{m\lambda }\] \[=\frac{6.6\times {{10}^{-34}}}{9.1\times {{10}^{-31}}\times {{10}^{-11}}}\] \[=7.25\times {{10}^{7}}m/s\] Energy of electron\[=\frac{1}{2}m{{v}^{2}}\] \[=\frac{1}{2}\times \frac{9.1\times {{10}^{-31}}\times {{(7.25\times {{10}^{7}})}^{2}}}{1.6\times {{10}^{-19}}}\] \[=15\text{ }keV\]


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