Radio Waves and Microwaves
Radio waves and microwaves are both types of electromagnetic radiation. They are made up of an electrical and a magnetic wave and they travel at the speed of light.
Both of these types of wave have important applications in modern life.
These are electromagnetic waves that have a wavelength of 1mm through to 1m. They were first proved to exist in 1888 by the German scientist Heinrich Hertz.
Microwaves are used in many applcations. In communication they are used to carry the signal in wireless and Bluetooth devices. Satellite communication also uses different frequencies of microwave radiation. Satellites also use microwaves for navigation applications. The Global Positioning System (GPS) uses microwave radiation for satellite navigation systems to locate themselves. Radar systems also use microwaves to locate objects.
Microwaves are also used in cooking food. The ability of microwaves to heat food was accidentally discovered by an American engineer called Percy Spencer in the 1940s. He was testing part of radar system when he found that the chocolate bar in his pocket began to melt. He realised that the microwaves were heating up the food and could be used in the kitchen. The scientific name for this process is called dielectric heating.
Microwave radiation can damage the body - usually when the shielding on a microwave oven doesn't work properly. The escaping radiation can damage the lens in the eye causing it to lose its transparency. This is called a cataract. Basically, it is 'cooking' the proteins in the eye in the same way as a cooked egg-white changes from transparent to white.
Radio waves have a slightly lower frequency (and a higher wavelength) than microwaves. The Ultra High Frequency (or UHF) waves are in the overlapping frequencies between microwaves and radio waves. The Very High Frequency (or VHF) waves have a lower frequency and are definitely in the radio wave spectrum. Both UHF and VHF waves are used to carry television signals. VHF has been used for many years for radio broadcasts, however, UHF signals are now being used as well in Digital Audio Broadcasting (or DAB radio).
Radio-frequency Identification (or RFID) is used in devices (often called tags) that can be tracked using suitable equipment. These tags can be used to track people, animals or used in security tags in shops.
RFID tags have been used to time the runners in races. In a marathon for example, where there are a large number of runners, it is would be impossible to time every person. But if they wear a small tag the computer can log the time that each runner takes to complete the course.
The 'chips' that are used in animal identification are RFID tags. A small tag, the size of a grain of rice, is injected under the skin of a dog, cat or horse. Each chip transmits a unique number which can be used to look up the details of that animal on a central database.
Libraries use RFID tags to keep track of the books that they own. You may have noticed a sticker placed in the inside cover of a book with a maze-like pattern in copper. This is the RFID tag.