Doppler Effect
Basic Definition
The doppler effect is the change in frequency of a wave depending on an observer moving corresponding to its source.
Background info/history
- - The doppler effect is named after christian doppler (1803-1853) who was an Austrian physicist and mathematician. He proposed this effect in 1842.
- - This phenomenon was tested for sound waves by Buys Ballot in 1845. He confirmed that the sound's pitch was higher than the emitted frequency when the source approached him, and lower than the emitted frequency when the source moved away from him.
- - Hippolyte Fizeau individually discovered the same phenomenon on electromagnetic waves in 1848; six years after Doppler's proposed it.
How it works/example
If you’ve ever waited to cross the street, you probably noticed that when a car goes past you, you can recognize a change in frequency of the sound from the car. As the car approaches you, the sound becomes higher in frequency and vise versa. At the instant the car passes you, the frequency drops noticabely.
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Trend
When a source of sound approaches an observer, the observed frequency increases.
When a source of sound moves away from an observer, the observed frequency decreases.
When a source of sound approaches an observer, the observed frequency increases.
When a source of sound moves away from an observer, the observed frequency decreases.