Which effect allows a police radar gun to measure the speed of a moving vehicle?
The radar compares the frequency of its transmitted radio wave with that of the wave reflected from the moving vehicle. The Doppler shift measures the component of the…
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Which effect allows a police radar gun to measure the speed of a moving vehicle?
Answer and explanation
Correct answer C
The radar compares the frequency of its transmitted radio wave with that of the wave reflected from the moving vehicle.
The Doppler shift measures the component of the vehicle's relative speed along the radar beam.
Option feedback
Option A
Electromagnetic induction concerns an induced voltage associated with changing magnetic flux. The radar derives speed from the frequency shift of its returned signal.
Option B
The Raman effect involves inelastic scattering related to energy exchanges with matter. The frequency shift measured by speed radar is caused by relative motion.
Option C
The Doppler shift of the reflected radio signal changes with the vehicle's speed along the radar beam.
Option D
Electrostatic force between charges does not explain the frequency shift of a radio wave reflected by a moving vehicle.
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