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Doppler effect Options
Posted: Monday, October 20, 2014 9:21:12 AM

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The Doppler effect is an effect observed in light and sound waves as they move toward or away from an observer. One simple example of the Doppler effect is the sound of an automobile horn. Picture a person standing on a street corner. A car approaches, blowing its horn. As the car continues moving toward the person, the pitch of the horn appears to increase; its sound goes higher and higher. As the car passes the observer, however, the effect is reversed. The pitch of the car horn becomes lower and lower.

All waves can be defined by two related properties: their wavelength and frequency. Wavelength is the distance between two adjacent (next to each other) and identical parts of the wave, such as between two wave crests (peaks). Frequency is the number of wave crests that pass a given point per second. For reference, the wavelength of visible light is about 400 to 700 nanometers (billionths of a meter), and its frequency is about 4.3 to 7.5 × 10 14 hertz (cycles per second). The wavelength of sound waves is about 0.017 to 17 meters, and their frequency is about 20 to 20,000 hertz.

The car horn effect described above was first explained around 1842 by Austrian physicist Johann Christian Doppler (1803–1853). To describe his theory, Doppler used a diagram like the one shown in the accompanying figure of the Doppler effect. As a train approaches a railroad station, it sounds its whistle. The sound waves coming from the train travel outward in all directions. A person riding in the train would hear nothing unusual, just the steady pitch of the whistle's sound. But a person at the train station would hear something very different. As the train moves forward, the sound waves from its whistle move with it. The train is chasing or crowding the sound waves in front of it. An observer at the train station hears more waves per second than someone on the train. More waves per second means a higher frequency and, thus, a higher pitch.

An observer behind the train has just the opposite experience. Sound waves following the train spread out more easily. The second observer detects fewer waves per second, a lower frequency, and, therefore, a lower-pitched sound.

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Posted: Tuesday, October 21, 2014 1:28:20 PM
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This is not to be confused with the "Dopeler effect", in which ideas seem smarter when they come at you faster.
Posted: Monday, January 26, 2015 9:39:38 AM

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Isn't that where you can duplicate someone. Ha
Posted: Monday, February 16, 2015 11:27:12 PM

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You are aware, I suppose, that cutting and pasting is illegal and stealing. It also adds nothing to this forum and is lazy.
Posted: Tuesday, February 17, 2015 12:31:31 PM

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I find no fault. Sheppie did give credit to her source.

early apex...Applause Applause Social media seems to have increased that effect.
Posted: Wednesday, February 18, 2015 12:33:44 PM
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Check the TFD copyright rule. Minor use is allowed if source given.
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