A radar used to detect the presence of aircraft receives a pulse that has reflected off an object $6\times 10^{-5}\text{ s}$ after it was transmitted. What is the distance from the radar station to the reflecting object?

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.