The higher frequency waves are electromagnetic waves. The famous scientist Maxwell mainly developed the complete theory of electromagnetic waves in 1864. Maxwell’s ideas was latterly experimented by Heinrich Hertz.
The famous Indian scientist Chandra Shekhar gave some of the facts. When the oscillating electric and the magnetic field is applied perpendicular to each other then the waves produced are known as electromagnetic waves. The direction of propagation of electromagnetic waves is perpendicular to both electric and magnetic fields applied. There are several types of electromagnetic waves based on the frequency such as extremely low frequency, low frequency, medium frequency, higher frequency, extremely higher frequency, etc.
Characteristics of Higher Frequency Waves:These waves have frequency between 3 hertz to 30 Mega hertz. These are used for the sky wave propagation. The propagation of radio waves signals of frequencies between 1500 kilo hertz to 30 Mega hertz form one place to another take place via reflection from ionosphere is called sky wave propagation.
Sky Wave Propagation of Higher Frequency Waves:The higher frequency wave propagation's is just equivalent to the total internal reflection from ionosphere. It can be explained by the general structure of ionosphere. In the ionosphere, the concentration of electrons increases with height and the result is decrease in refractive index. If the whole region of the ionosphere is divided into different layers of different electronic density then the direction of ray would be altered by successive refractions that it would be strike each succeeding layer more and more oblique.
Eventually it will strike a layer at an angle just greater than critical angle where the ray would be totally reflected. The down coming ray will be able to actuate a radio receiver at a point on earth where it returns now on reaching the earth’s surface it reflected like a light ray from the mirror, and goes up again at the same angle at which it started on reaching the ionosphere it is again refracted, suffers total internal reflection and come back to the earth at a point twice as far from the transmission as that at which it first came down. This process is repeated until the whole energy of higher frequency waves dies down.