Radar

[|Radar] - a system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. Radar was originally called RDF (Radio Direction Finder).

[|Radar waves] reflection depends on the size of the radio wave and the shape of the target.
 * if the radio wave is much shorter than the reflector's size, the wave will bounce off in a way similar to the way light bounces from a mirror. Early radars used very long wavelengths that were larger than the targets and received a vague signal
 * modern systems use shorter wavelengths (a few centimetres) that can image objects as small as a loaf of bread

A solid object will usually reflect radar waves. This is particularly true of electrically-conductive materials such as metal, making radar particularly well suited to the detection of aircraft and ships.

[|Radar] is use to detect where something is, where it’s going and how fast it’s moving. Radar has a transmitter that produces radio waves and a receiver that detects them. The system first sends out radio waves. The waves hit an object and some get reflected back toward the radar. As they return, the waves are picked up by the radar’s receiver. The time that it takes for the waves to come back and how the waves have changed when they return provides useful information about the object ahead. This is a radar antenna on top of a boat. It emits a rotating beam of signals to help detect other boats (and avoid hitting them).

A solid object will usually reflect radar waves. This is particularly true of electrically-conductive materials such as metal, making radar particularly well suited to the detection of aircraft.
 * What's the problem?**
 * **Ask** - Tracking the location of aircraft is important. They may be in locations where they can't be seen even with telescopes. Where are the aircraft? What would help aircraft avoid thunderstorms and other aircraft, as well as towers and tall buildings?
 * **Imagine** - It would be great to have super-vision to be able to see airplanes even in the fog and in clouds. What are some of the problems with just looking out the window? What would be super-vision be able to "see"? What are some of the properties of radar that can provide these capabilities?
 * **Design, Build** - The electronics for radar systems generate at waves, send them out toward the target and detect the reflections as they occur. The farther away the target is, the longer it takes for the reflection to return. The radar system can then determine the range, altitude, direction, or speed of the target. How would this information be used to to avoid aircraft collisions?
 * **Improve** - In order to have high resolution, the radar waves must be short. When does this matter?


 * That's engineering**
 * [|electromagnetic field] - a field composed of two related fields —the electric field and the magnetic field.
 * [|wavelength] - the distance between repeating units of a wave pattern.

> electromagnetic waves, range, altitude, direction, speed, reflect, electrically-conductive materials, wavelength
 * Engineering ideas**

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