A ground receiver receives a signal at 5 MHz , transmitted by a ground transmitter at a height of 320 ~m , which is 110 ~km away from it. Then it can communicate through (radius of earth R=6400 ~km )

Step-by-step solution

Maximum distance covered by space wave communication = 2 R h = 2 (6400 10^3 ~m )(320 ~m ) =64 ~km Since the distance between transmitter and receiver is 110 ~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 aligned v_c & =9 (N_ )^ 1 / 2 =9 (10¹² )^ 1 / 2 & =9 10^6 ~Hz =9 MHz aligned where, N_ = Maximum electron density of ionosphere. As the signal frequency 5 MHz < 9 MHz , so the communication is through sky