Question

A plane electromagnetic wave travels in a medium of relative permeability $1.61$ and relative permittivity $6.44$. If magnitude of magnetic intensity is $4.5\times 10^{-2}A{m}^{-1}$ at a point, what will be the approximate magnitude of electric field intensity at that point ?
(Given : permeability of free space ${\mu }_0=4\pi \times 10^{-7}N{A}^{-2}$, speed of light in vacuum $c=3\times 10^{8}m{s}^{-1}$ )

• A. $16.96V{m}^{-1}$
• B. $2.25\times 10^{-2}V{m}^{-1}$
• C. $8.48V{m}^{-1}$
• D. $4.2\times 10^6$

Answer 1

Answer: (D)

${\mu }_r=1.61$
${ϵ}_r=6.44$
$B=4.5\times 10^{-2}$
$E=?$
$C=\frac{1}{\sqrt{{\mu }_0{ϵ}_0}}V=\frac{1}{\sqrt{\mu \in }}$
$\frac{C}{V}=\sqrt{{\mu }_r{\in }_r}=\sqrt{1.61\times 6.44}$
$\frac{E}{B}=V=\frac{3\times 10^8}{\sqrt{1.61\times 6.44}}=9.32\times 10^{7}m/s$
$E=4.5\times 10^{-2}\times 9.32\times 10^7$
$=4.2\times 10^6$