Why does the pitch of an airplane sound like it goes from high to low when it flies overhead?
In: Physics
As others have said, that is the dopler effect, but it was not just airplanes.
The same thing happens with horns and sirens on trains and automobiles.
It even affects radio waves coming from fast moving objects. I don’t mean a car or truck with a CB radio. I mean, the affect is there, but cars and trucks moving on the highway can’t move fast enough for the dopler effect to be noticeable. But satellites and space vehicles in orbit _are_ moving fast enough for the dopler effect to be noticeable.
The satellite must be moving, relative to the observer. If it is, when the satellite is moving towards the observer the dopler effect will cause the satellite transmitter frequency to seem higher than it really is. When the satellite is moving away from the observer the satellite transmitter frequency will seem lower than it really is.
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