Question

Which type of communication is employed in mobile phones?

Answer 1

Hint: The waves that are used in mobile phones are radio waves and there are different routes for its propagation.
The waves employed are emitted by a transmitter and received by a receiver.

Complete step by step answer:
Block diagram showing system of communication

Different ways to propagate the signal are:
1.Sky wave propagation: The signals emitted by a transmitter on the earth gets reflected by the ionosphere (a layer of the atmosphere) and is received by the receiver on earth. It is used for the propagation of waves of the frequency range between 30-40 MHz

2. Space wave propagation: This transmission is limited to the line of sight (from tower to tower). Waves generally travel in a straight line from the transmitter to the receiver. It is used for propagation of waves of frequency greater than 40 MHz. Diagrammatically, transmitter (T) and receiver towers can be shown as:

3. Ground wave propagation: Low-frequency waves are transmitted over the surface of the earth (waves gliding the surface of the earth). The range is less due to the absorption by mountains, rocks, etc. present on the surface.
🡪All the above propagation ways can be employed for mobile phone communication

But the prominently used are sky wave and space wave. Ground wave is not used because of its less range, it is used in landlines.

Note:In case of sky wave propagation, if the frequency is more than 40 MHz, instead of reflection, refraction takes place and the waves are not received by the receiver.
In sky wave propagation satellites are used for higher frequencies e.g. television broadcast