JEE Main & Advanced Physics Wave Optics / तरंग प्रकाशिकी Question Bank EM Waves

  • question_answer
    If c is the speed of electromagnetic waves in vacuum, its speed in a medium of dielectric constant K and relative permeability \[{{\mu }_{r}}\] is                                                                  [Kerala PET 2005]

    A)            \[v=\frac{1}{\sqrt{{{\mu }_{r}}K}}\]                               

    B)            \[v=c\sqrt{{{\mu }_{r}}K}\]

    C)            \[v=\frac{c}{\sqrt{{{\mu }_{r}}K}}\]                               

    D)            \[v=\frac{K}{\sqrt{{{\mu }_{r}}C}}\]

    Correct Answer: C

    Solution :

                       Speed of light of vacuum \[c=\frac{1}{\sqrt{{{\mu }_{0}}{{\varepsilon }_{0}}}}\] and in another medium \[v=\frac{1}{\sqrt{\mu \varepsilon }}\] \ \[\frac{c}{v}=\sqrt{\frac{\mu \varepsilon }{{{\mu }_{0}}{{\varepsilon }_{0}}}}=\sqrt{{{\mu }_{r}}K}\] Þ \[v=\frac{c}{\sqrt{{{\mu }_{r}}K}}\]


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