JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank Critical Thinking

  • question_answer
    The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is [MNR 1994; MP PMT 1994]

    A)            1/2

    B)            2/137

    C)            1/137                                       

    D)            1/237

    Correct Answer: C

    Solution :

                       Speed of electron in nth orbit of hydrogen atom \[v=\frac{{{e}^{2}}}{2{{\varepsilon }_{0}}n\,h}\] In ground state n = 1 Þ \[v=\frac{{{e}^{2}}}{2{{\varepsilon }_{0}}h}\] Þ \[\frac{v}{c}=\frac{{{e}^{2}}}{2{{\varepsilon }_{0}}ch}=\frac{{{(1.6\times {{10}^{-19}})}^{2}}}{2\times 8.85\times {{10}^{-12}}\times 3\times {{10}^{8}}\times 6.6\times {{10}^{-34}}}\]\[=\frac{1}{137}\].


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