Propagation of Electromagnetic Waves I Video Lecture - Civil Engineering (CE)

propagation of electromagnetic waves in
communication using radio waves an
antenna at the transmitter radiates the
electromagnetic waves
ium waves which traveled through the
space and reach the receiving antenna at
the other end as the e/m wave travels
away from the transmitter the strength
of the wave keeps on decreasing several
factors influence the propagation of e/m
waves and the path they follow at this
point it is also important to understand
the composition of the Earth's
atmosphere as it plays a vital role in
the propagation of e/m waves ground wave
to radiate signals with high efficiency
the antennas should have a size
comparable to the wavelength lambda of
the signal at least approximately lambda
by 4 at longer wavelengths that is at
lower frequencies the antennas have
large physical size and they are located
on or very near to the ground in
standard AM broadcast ground-based
vertical travels are generally used as
transmitting antennas for such antennas
ground has a strong influence on the
propagation of the signal the mode of
propagation is called surface wave
propagation and the wave glides over the
surface of the earth Aviv induces
current in the ground over which it
passes and it is attenuated as a result
of absorption of energy by the earth the
attenuation of surface waves increases
very rapidly with increasing frequency
the maximum range of coverage depends on
the transmitted power and frequency less
than a few megahertz
sky waves
in frequency range from a few megahertz
up to 30 to 40 megahertz long distance
communication can be achieved by I know
spheric reflection of radio waves back
towards the earth this mode of
propagation is called skywave
propagation and is used by shortwave
broadcast services the ionosphere is so
called
because of the presence of a large
number of ions or charged particles it
extends from a height of about 65
kilometers to about 400 kilometers above
the Earth's surface
ionization occurs due to the absorption
of the ultraviolet and other high-energy
radiation coming from the Sun by air
molecules the ionosphere is further
subdivided into several layers