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Q.
Calculate the phase velocity of electromagnetic wave having electron density and frequency for $D$ layer, $N=400$ electron $/ cm ^{3}, v =300\, kHz$
Communication Systems
Solution:
$: \mu=\mu_{0} \sqrt{1-\frac{81.45 N}{v^{2}}}$
Here, $N=400$ electron $cm ^{-3}=400 \times 10^{6}$ electron $m ^{-3}$
$v =300 kHz =300 \times 10^{3} Hz ,$ and $\mu_{0}=1$
$\Rightarrow \mu=1 \sqrt{1-\frac{81.45\left(400 \times 10^{6}\right)}{\left(300 \times 10^{3}\right)^{2}}}=0.8$
$\Rightarrow c=\frac{c_{0}}{\mu}=\frac{3 \times 10^{8} ms ^{-1}}{0.8}=3.75 \times 10^{8} ms ^{-1}$