Question
A radar used to detect the presence of aircraft receives a pulse that has reflected off an object after it was transmitted. What is the distance from the radar station to the reflecting object?
Final Answer
Solution video
OpenStax College Physics for AP® Courses, Chapter 24, Problem 13 (Problems & Exercises)
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Video Transcript
This is College Physics Answers with Shaun Dychko. This radar emits a pulse of light and that's reflected-off this aircraft and returns to the radar sometime later. And so we want to find how far is the aircraft from the radar given a certain amount of time it takes to do this round trip; while doing the round trip means doing the trip twice. So covering this distance d twice and so we have 2 times the distance between the aircraft in the radar equals the speed of this wave, which is the speed of light c multiplied by the total time it takes to do the round trip. And so we'll divide both sides by 2 to solve for d. And we get d then is the speed of light 3 times 10 to the 8 meters per second multiplied by the time between emission and detection of the reflected pulse, which is 6 times 10 to the minus 5 seconds and divide that by 2 to get a distance of 9 kilometers and only one significant figure is appropriate here because our time measurement is one significant figure.