What is propagation model? Describe the characteristics of ground, sky and space wave.
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Answer:
What is Electromagnetic Wave Propagation?

Electromagnetic Waves also called Electromagnetic Radiations are basically defined as superimposed oscillations of an Electric and a Magnetic Field in space with their direction of propagation perpendicular to both of them. In simple words, electromagnetic waves are oscillations produced due to crossing over of an electric and a magnetic field.
The direction of the propagation of such waves is perpendicular to the direction of the force of either of these fields as seen in the above figure. Like all waveforms, these have some properties as well. Let us have a look at the properties of electromagnetic wave propagation.
Properties of Electromagnetic Wave Propagation
These waves travel at the speed of light.
These waves do not require any medium for propagation.
Electromagnetic waves travel in a transverse form.
Electromagnetic waves are not deflected by electric or magnetic field.
These waves can be polarized.
Electromagnetic Waves undergo interference and diffraction.
The wavelength(λ) and frequency (v) of the EM waves can be related as:
c= v.λ
where c = velocity of the wave. To study the electromagnetic wave propagation let us study the example of production of X rays.
Xrays are electromagnetic waves having a wavelength range of 0.001 nanometers to 10 nanometers ( 1 nanometre =10^-9 meter). They find a wide variety of applications ranging from medical purposes like detection of an anomaly inside a body to security at airports or public places.
X rays are generated inside an Xray tube which is nothing but a tube with a vacuum that has a high potential difference at its ends. This causes a stream of high-velocity electrons to hit a target anode mostly tungsten or another metal depending on the type of wavelength required.
As the electrons collide with the target they transmit the high energy they possess in form of photons to the anode thus generating Xrays. Now let us study some methods of propagation of EM waves: Mesosphere, Troposphere, Ionosphere are the different layers.