(i) Ground waves- the ground waves which progress along the surface of the earth are called ground waves or surface waves.The ground propagation is suitable for low and medium frequency. i.e., up to 2 MHz only, hence it is also called medium ware propagation The maximum range of ground or surface wave propagation depends on : 

(a) The frequency of the radio waves and 

(b) power of the transmitter.

(ii) The sky waves-The sky waves are the radio waves of frequency between 2MHz to 30 MHz. The ionosphere reflects those radio waves so that they can propagate through atmosphere. The sky wave propagation is also known as ionosphere propagation.

The sky waves are used for very long distance radio communication at medium high frequencies (i.e. at medium waves and short waves.) The radio waves can cover a distance opproximately 400 km in a single reflection from the ionosphere.

(iii) Space wave- The space waves are the radio waves of very high frequency (i.e. between 30 MHz to 300 MHz or more). The space waves can travel through atmosphere form transmitter antena to receive antenna eighter directly or after reflection from ground in the earth's troposphere region. lt is also called Tropospherical propagation or line of sight propagation. this propagation is limited (a) to the line of sight distance. (b) by the curvature of the earth.

It is utilized in T.V. communication, radar communication etc.