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A ground receiver receives a signal at $5 \mathrm{MHz}$, transmitted by a ground transmitter at a height of $320 \mathrm{~m}$, which is $110 \mathrm{~km}$ away from it. Then it can communicate through (radius of earth $R=6400 \mathrm{~km}$ )
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The correct answer is:
sky waves
Maximum distance covered by space wave communication
$=\sqrt{2 R h}=\sqrt{2\left(6400 \times 10^3 \mathrm{~m}\right)(320 \mathrm{~m})}=64 \mathrm{~km}$
Since the distance between transmitter and receiver is $110 \mathrm{~km}$, therefore the given frequency signal cannot communicate through either by ground waves or space waves.
For sky wave, the value of critical frequency is
$\begin{aligned} v_c & =9\left(N_{\max }\right)^{1 / 2}=9\left(10^{12}\right)^{1 / 2} \\ & =9 \times 10^6 \mathrm{~Hz}=9 \mathrm{MHz}\end{aligned}$
where, $N_{\max }=$ Maximum electron density of ionosphere.
As the signal frequency $5 \mathrm{MHz} < 9 \mathrm{MHz}$, so the communication is through sky waves.
$=\sqrt{2 R h}=\sqrt{2\left(6400 \times 10^3 \mathrm{~m}\right)(320 \mathrm{~m})}=64 \mathrm{~km}$
Since the distance between transmitter and receiver is $110 \mathrm{~km}$, therefore the given frequency signal cannot communicate through either by ground waves or space waves.
For sky wave, the value of critical frequency is
$\begin{aligned} v_c & =9\left(N_{\max }\right)^{1 / 2}=9\left(10^{12}\right)^{1 / 2} \\ & =9 \times 10^6 \mathrm{~Hz}=9 \mathrm{MHz}\end{aligned}$
where, $N_{\max }=$ Maximum electron density of ionosphere.
As the signal frequency $5 \mathrm{MHz} < 9 \mathrm{MHz}$, so the communication is through sky waves.
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