Scientists Say: Radar
Radar (noun, “RAY-dar”)
This is a system people 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.
The word “radar” comes from the U.S. Navy. It was an acronym — or a word made out of the starting letters from a group of words. RADAR stood for RAdio Direction And Ranging. But now it’s been used so much that “radar” is a word on its own.
In a sentence
Scientists can use radar to find out how deep the ocean is — taking measurements that are accurate to within one centimeter (0.39 inch).
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acronym A word made by combining some of the starting letter or groups of letters from a number of words. For instance, STEM is an acronym for Science, Technology, Engineering and Math. Radar is an acronym for RAdio Detection And Ranging. Even laser is an acronym for Light Amplification by Stimulated Emission of Radiation.
radar A system for calculating the position, distance or other important characteristic of a distant object. It works by sending out periodic radio waves that bounce off of the object and then measuring how long it takes that bounced signal to return. Radar can detect moving objects, like airplanes. It also can be used to map the shape of land — even land covered by ice.
radio To send and receive radio waves, or the device that receives these transmissions.
radio waves Waves in a part of the electromagnetic spectrum. They are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar.
wave A disturbance or variation that travels through space and matter in a regular, oscillating fashion.