ASTRO-110 Lecture Notes - Lecture 27: Christian Doppler, Flatcar, Absolute Pitch
18 Sep 2020
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Document Summary
There is an everyday phenomenon that is so common you probably don"t even pay attention to it any more. A car or truck goes past you on the street and the whine of its motor is high pitched as it approaches you and as it passes and goes away the pitch is lowered. It is more noticeable when the sound is less complex like a train whistle. The faster the source of the sound moves past you the more pronounced is the change in the pitch. This is known in science as the doppler effect. The whistle is not actually changing its frequency (which is the scientific measurement of the pitch); the driver of the car notices no such effect. It is only an observer who is at rest with respect to a moving source who observes the effect. The doppler effect is named for christian doppler (1803-1853) an austrian physicist.
