JEE Main & Advanced Sample Paper JEE Main - Mock Test - 3

  • question_answer
    The dimension of \[\frac{{{e}^{2}}}{4\pi {{\varepsilon }_{0}}hc},\]where e, \[{{\varepsilon }_{0}},\] h and c are electric charge, electric permittivity, Planck's constant and velocity of light in vacuum respectively, is

    A) \[[{{M}^{0}}{{L}^{0}}{{T}^{0}}]\]         

    B) \[[M{{L}^{0}}{{T}^{0}}]\]

    C) \[[{{M}^{0}}L{{T}^{0}}]\]         

    D) \[[{{M}^{0}}{{L}^{0}}T]\]

    Correct Answer: A

    Solution :

    From \[F=\frac{1}{4\pi {{\varepsilon }_{0}}}\,\frac{{{e}^{2}}}{{{r}^{2}}}\] \[\therefore \,\,\frac{{{e}^{2}}}{{{\varepsilon }_{0}}}=4\pi \,F\,{{r}^{2}}\] (dimensionally)                    \[\frac{{{e}^{2}}}{{{\varepsilon }_{0}}hc}=\frac{F{{r}^{2}}}{hc}=\frac{(ML{{T}^{-2}}){{L}^{2}}}{M{{L}^{2}}{{T}^{-1}}(L{{T}^{-1}}]}=[{{M}^{0}}{{L}^{0}}{{T}^{0}}]\],


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