In the latter part of the nineteenth century electricity and magnetism were a prime area of research in Europe. In 1887, Heinrich Hertz in Germany was the first to realize the significance of the behavior of radiowaves. Hertz found that, like most electromagnetic waves, radio waves could be deflected and reflected by certain materials. Physicists knew that radio waves traveled at a constant 298,051 km/s (186,282 mi/s). If the returning radio waves arrived one second after leaving, then the reflecting object was 149,025 km (93,141 mi) away. The technology that used this principle was developed during the 1930s by the British team led by Sir Robert Watson-Watt, who called it RAdio Detection and Ranging, or RADAR. It was incredibly useful in 1940, when Britain was at war with Germany, as it enabled the British air force to know in advance the position of enemy aircraft even if they were invisible due to cloud cover, darkness or just large distance.
Radar systems consist of four basic parts. A transmitter generates the radio signal. An antenna directs the signal toward the target and captures the reflected signal. A receiver takes the reflected signal from the antenna and processes it. Finally, a display unit takes the processed signal and displays it in such a way that the radar operator can interpret the signal's information.
Radar operates using the physical principles of electromagnetic radiation—energy that moves in wavelike forms at the speed of light or less. Most radar systems use energy that falls in the longer wavelength area of the electromagnetic spectrum, in the same general area as microwave and radio radiation: beyond the wavelengths of visible light. Radar systems use these wavelengths because they tend not to scatter as easily as shorter waves, such as x rays or gamma rays, and a greater percentage of the electromagnetic signal can be received by the unit. Different systems can use different wavelengths, depending on the type of object or phenomena they are trying to detect. Some long-wavelength radar systems can even bounce signals off the earth's ionosphere, providing important information about the atmosphere and the weather.
Radar has many uses in the modern world. The same idea is now used in guidance systems for aircraft and rockets. Doppler radar is used for used for weather forecasting, since storm clouds reflect certain radio waves. Radar can also be used to measure the motion or speed of the detected object. The police have used radar devises to detect the speed of oncoming vehicles for many years. Computers can process the echo of a radar signal, removing a lot of the "noise" or "clutter" and revealing the fundamental shape of the object that is reflecting the signal, which can benefit aircraft controllers and anti-ballistic missile defense systems
This is the complete article, containing 457 words
(approx. 2 pages at 300 words per page).
