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 $4.5 \times 10^{-2} \,Am ^{-1}$ at a point, what will be the approximate magnitude of electric field intensity at that point ?
(Given : permeability of free space $\mu_{0}=4 \pi \times 10^{-7}\,NA ^{-2}$, speed of light in vacuum $c =3 \times 10^{8} \,ms ^{-1}$ )

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

Answer 1

Answer: (D)

$\mu_{ r }=1.61 $
$\epsilon_{ r }=6.44$
$B =4.5 \times 10^{-2}$
$E =?$
$C =\frac{1}{\sqrt{\mu_{0} \epsilon_{0}}} V =\frac{1}{\sqrt{\mu \in}}$
$\frac{ C }{ V }=\sqrt{\mu_{ r } \in_{ r }}=\sqrt{1.61 \times 6.44}$
$\frac{ E }{ B }= V =\frac{3 \times 10^{8}}{\sqrt{1.61 \times 6.44}}=9.32 \times 10^{7} \,m / s$
$E =4.5 \times 10^{-2} \times 9.32 \times 10^{7}$
$=4.2 \times 10^{6}$