Radar signals are radio waves emitted by an object or animal that is used to detect objects in the atmosphere or underwater. These signals are one of the primary ways to detect weather and monitor air traffic. Radar stands for radio detection and ranging.
Radar signals start from a transmitter, which sends out the signal. In some cases, there is no specific object targeted. In other cases, specific objects may be targeted, especially in military applications. Once the radar hits the object, most of the radio signals scatter, but a few are reflected back to a receiver. This is called an echo. This is then outputted, usually on a monitor, to an individual responsible for monitoring the results, such as a meteorologist or air traffic controller.
Radar signals travel at the speed of light, or very near it, and thus the feedback is nearly instant. Radar can not only let someone know that an object is present, but also indicate its distance from the transmitter and receiver, its speed, and it's altitude as well. Due to the speed of radar signals, they must be measured with very precise equipment in order to determine distance and speed.
Radar signals are especially useful in military applications to show the presence of aircraft. If the aircraft is hostile, early warning through the use of radar allows countermeasures to be taken in an attempt to thwart an attack. Because airplanes are usually made of metal, they are especially prone to being detected by radar.
This vulnerability to radar detection has led some governments to design ways to avoid being spotted. One way may be to build planes using a different material that does not reflect radar signals, but rather absorbs most of them. The entire plane can be built of such material, or it may be possible to coat the aircraft with a substance that avoids radar signals. Radar signals can also be jammed by those sending radar signals back to a receiver, which will indicate false echoes over a wide geographic range and render the radar useless for the detection of specific objects.
In addition to air traffic monitoring, another common use for radar is in weather detection. Radar can indicate a number of different factors regarding weather, including cloud cover and the intensity of precipitation falling. Some radar systems are even able to determine the type of precipitation that is falling.