Radio waves are reflected and refracted in the Earth’s atmosphere:
––the amount of refraction depends on the frequency of the wave
––there is less refraction at higher frequencies
Radio stations broadcast signals with a particular frequency
The same frequency can be used by more than one radio station:
––the radio stations are too far away from each other to interfere
––but in unusual weather conditions, the radio waves can travel
further and the broadcasts interfere.
Interference is reduced if digital
signals are used.
Wireless technology is used by:
––radio and television ––laptops
Digital Audio Broadcasting or DAB also provides a greater choice of
radio stations but the audio quality is not as good as the FM signals
currently used.
DAB eliminates interference between other radio stations
Radio Reflection
Radio waves are reflected from the ionosphere. They
behave like light in an optical fibre and undergo total
internal reflection.
Microwaves pass through the
ionosphere.
Communication satellites orbit above the equator
and take 24 hours to orbit Earth
Water reflects radio waves but land mass
does not.
Continued reflection by the ionosphere and the
oceans allows radio waves to be received from an
aerial that is not in line of sight.
Microwave signals are
received by orbiting satellites,
amplified and retransmitted
back to Earth.
Communication Problems
The transmitting aerial needs to send a focused beam to the
satellite because its aerial is very small.
The transmitted beam is
slightly divergent.
Some energy is lost from the edge of the transmitting
aerial because of diffraction
Radio waves are diffracted when
they meet an obstruction
Refraction in the atmosphere needs to be
taken into account when sending a signal to a
satellite.