Question

A ground received 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) 

(a) space waves

(b) ground waves 

(c) sky waves  

(d) both sky and ground waves

Answer 1

The correct option is (c) sky waves.

Explanation:

Maximum distance covered by space wave communication

Since the distance between transmitter and receiver is 110 km, therefore the given frequency signal cannot communicate through either by ground waves or space wave, 

For sky waves, the value of critical frequency is

where, N_max = Maximum electron density of ionosphere. 

As the signal frequency 5 MHz < 9 MHz, so the communication is through sky waves.