An electromagnetic wave of frequency $5\, GHz ,$ is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are $2 .$ Its velocity in this medium is $\times 10^{7}\, m / s$

  • [JEE MAIN 2021]
  • A

    $12$

  • B

    $18$

  • C

    $15$

  • D

    $20$

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