Radio Waves-
Radio waves are commonly used for communication purposes. They have the longest wavelengths in the electromagnetic spectrum. Radio waves not only bring music to your radio, they can also carry signals to your television and mobile phones. The antenna on the top of most homes is set to receive signals from Television Broadcasters, in the form of electromagnetic waves. These waves are then produced as images on the television screen.
Short-wave radio signals can be transmitted long distances by beaming the wave upwards and at an angle. The waves are then reflected back to Earth by the ionosphere (outermost layer of the atmosphere), far away from the transmitter.
Radio waves have frequencies from 300 GHz to as low as 3 kHz, and wavelengths that range from 1 millimeter to 100 kilometers.
There are 2 main types of radio waves:
AM radio waves
Waves used to carry radio signals between 540 and 1600 kHz. Information is carried by amplitude variation. They can travel further than FM signals and go around buildings, trees and hills but are more likely to suffer from interference.
FM radio waves
Waves used to carry radio signals between 88 and 108 MHz. Information is carried by frequency modulation.
If there is an obstacle that is hard for the radio wave to pass through, on the other side of this obstacle, the radio wave becomes weak, it refracts and feedback occurs.
Short-wave radio signals can be transmitted long distances by beaming the wave upwards and at an angle. The waves are then reflected back to Earth by the ionosphere (outermost layer of the atmosphere), far away from the transmitter.
Radio waves have frequencies from 300 GHz to as low as 3 kHz, and wavelengths that range from 1 millimeter to 100 kilometers.
There are 2 main types of radio waves:
AM radio waves
Waves used to carry radio signals between 540 and 1600 kHz. Information is carried by amplitude variation. They can travel further than FM signals and go around buildings, trees and hills but are more likely to suffer from interference.
FM radio waves
Waves used to carry radio signals between 88 and 108 MHz. Information is carried by frequency modulation.
If there is an obstacle that is hard for the radio wave to pass through, on the other side of this obstacle, the radio wave becomes weak, it refracts and feedback occurs.
In today's society we use:
Satellite Technology When used for communications, a satellite acts as a repeater. Its immense height above the Earth means that signals can be transmitted over large distances much greater than the line of sight. The Earth Station, transmits the signal up to the satellite. This is known as the up-link and it is transmitted on one frequency. The satellite receives the signal and retransmits it, on what is called the down-link, which is on another frequency. Satellites are used for various different reasons like:
etc. Specifically navigation satellites-- Scientists at the John Hopkins University's Applied Physics Laboratory monitored a satellite. They noticed that when the transmitted radio frequency was plotted on a graph, a pattern developed. It was known as the doppler effect. The doppler effect is a recognisable change of radio frequency as something that emits a signal in the form of waves passes by. Eg: hearing a change in pitch when a siren goes past you on the road. The lowering of the frequency as the police car passes you. Today, most navigation devices use time and distance to determine your location. They then use a intricate computer system to study the data and pinpoint the exact position on a map. Given the velocity and the time required for a radio signal to be transmitted between two points, the distance between the two points can be worked out using the equation: velocity = distance travelled / by time taken. |
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