Wednesday, July 6, 2011

Radio Waves - Millie Thng 07

Radio waves are an invisible form of electromagnetic radiation that varies in wavelength

Electromagnetic waves do not require a medium to travel

Radio waves are given off by stars, sparks and lightning, which is why you hear interference on your radio during a thunderstorm

"Radio" is a term describing all forms of electromagnetic radiation with a wavelength longer than a millimeter and a frequency above 300 GHz

Radio waves are divided into 4 groups :

Long Wave - around 1 to 2 km in wavelength

Medium Wave - around 100m in wavelength

VHF (Very high frequency) - wavelengths of around 2m

UHF (Ultra High Frequency) - wavelengths of less than a metre

Radio waves with a wavelength of less than around 10 meters are absorbed by the atmosphere. Otherwise, they bounce back and forth between the ionosphere and the ground, making radio ideal for transmitting over the horizon

Radio is one of our most important ways of communicating. Since the late 1800s, when radio was invented, it has played a huge role in our lives. Communication between two far distant places became quick and much more inexpensive than stringing telegraph wire

Commercial vehicles such as taxis, trucks, and airplanes use radios to receive directions and report difficulties. Construction crews, farmers, ranchers, and other groups use radio to send and receive information such as instructions and warnings. Radio is used extensively in the military to facilitate communication between bases, ships, planes, military vehicles, and field units

Broadcasting is the most well known use of radio. Radio stations arrange songs and programs of particular genres to broadcast to listeners who tune in to hear them. Most stations provide short newscasts and talk radio provides a public forum where people can listen to interviews or call in to speak with the host or his or her guests. Sports events can be broadcast as an announcer provides a play-by-play description of the action. Companies can buy ad space on privately owned stations to air commercials designed to appeal to that station's listeners

Two-way radios are also very important. Emergency personnel such as police, fire fighters, and ambulance crews use radio to stay in contact with their bases and with each other. They send and receive reports with radios in their vehicles and carry smaller portable devices with them. An EMT can send descriptions of wounded individuals ahead to the doctors at a hospital so they can prepare to treat them

Other uses of radio include remote controls used to direct toys, railroad cars, or unpiloted aircraft. Airplanes depend on radioed navigation signals to stay on course and a form of radio called radar is used to guide ships, submarines, and aircraft as well as to detect them. Radios may also transmit large amounts of data between electronic devices, such as computers. Devices called bugs allow others to listen in on private conversations to obtain information and are commonly used by intelligence agencies. Doctors can also use radio to diagnose stomach ailments by having the patient swallow a capsule radio and then studying the signals it transmits

However, radio waves may be dangerous too Large doses of radio waves are believed to cause cancer, leukaemia and other disorders Some people claim that the very low frequency field from overhead power cables near their homes has affected their health

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