NEET Physics Mathematical Tools, Units & Dimensions Question Bank Assertion and Reasons

  • question_answer
    Assertion:         The quantity \[(1/\sqrt{{{\mu }_{0}}{{\varepsilon }_{0}}})\] is dimensionally equal to velocity and numerically equal to velocity of light. Reason:           \[{{\mu }_{0}}\] is permeability of free space and \[{{\varepsilon }_{0}}\]is the permittivity of free space.

    A)   If both assertion and reason are true and the reason is the correct explanation of the assertion.

    B)    If both assertion and reason are true but reason is not the correct explanation of the assertion.

    C)     If assertion is true but reason is false.

    D)      If the assertion and reason both are false.

    E)        If assertion is false but reason is true.

    Correct Answer: B

    Solution :

                    Both assertion and reason are true but reason is not the correct explanation of assertion. \[[{{\varepsilon }_{0}}]=[{{M}^{-1}}{{L}^{-3}}{{T}^{4}}{{I}^{2}}]\],  \[[{{\mu }_{0}}]=[ML{{T}^{-2}}{{I}^{-2}}]\] \[\Rightarrow \frac{1}{\sqrt{({{\mu }_{0}}/4\pi )\times 4\pi {{E}_{0}}}}=\sqrt{\frac{9\times {{10}^{9}}}{{{10}^{-7}}}}=\sqrt{9\times {{10}^{16}}}\] \[=3\times {{10}^{8}}m/s.\]            Therefore \[\frac{1}{\sqrt{{{\mu }_{0}}{{\varepsilon }_{0}}}}\] has dimension of velocity and numerically equal to velocity of light.


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