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Q.
A plane electromagnetic wave $E_{z}=100 \cos \left(6 \times 10^{8} t+4 x\right) V / m$
propagates in a medium. The refractive index of the medium is
Electromagnetic Waves
Solution:
Comparing the given equation with the equation of plane electromagnetic wave, we get
$E_{z}=E_{0} \cos (\omega t+k x) \therefore \omega=6 \times 10^{8}$ and $k=4$
Velocity of light in medium,
$v=\frac{\omega}{k}=\frac{6 \times 10^{8}}{4}=\frac{3}{2} \times 10^{8}\, m / s$
Refractive index, $\mu=\frac{c}{v}=\frac{3 \times 10^{8}}{(3 / 2) \times 10^{8}}=2$