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Radar
Intermediate
Uses reflected radio waves to measure range and speed.
Radar sends radio pulses and times the echo: distance = ct/2. Doppler shift gives velocity. Used for air traffic, weather and speed cameras.
An echo delay of 100 μs means 15 km.
Stealth aircraft reduce the echo.
In more detail
Radar sends pulses of microwave or radio waves and detects their reflections from objects. The time delay gives distance, and the Doppler shift gives speed.
Real-world uses
- Air traffic control uses radar to track aircraft.
- Weather radar detects rain and storm movement.
- Air traffic control and police speed cameras use radar to measure distance and speed from reflected radio waves.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
How is distance found?
Half the round-trip time multiplied by the speed of light.
How does radar measure speed?
From the Doppler shift in the reflected frequency.
How does radar find speed?
The Doppler shift in the reflected wave gives the speed of the moving object.
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