Law enforcement officers use radar guns based on the Doppler effect to measure the speed of automobiles. Explain why the details of the Doppler effect make it desirable for the officers to park near the road in a place without curves
What will be an ideal response?
The Doppler effect uses a measured change in the wavelength of photons to determine the speed of an object. The effect is only able to detect motion toward or away from the receiver, not motion directed side to side.
If the officer positioned himself far from the roadway, he would be viewing an oncoming car from an angle. In this situation, part of the velocity of the automobile would be side-to-side across the officer's line of sight. The Doppler effect would measure only the velocity of the car along the line of sight, and underestimate the true speed of the car. If the road was curved, the same situation would apply.
The officer can only get a true measure of the car's velocity if the velocity of the car is directly along the line of sight.
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