DOPPLER EFFECT AND SONIC BOOM Teacher: Ms. Kathleen Booth Subject: PhysicsPresented By: SANGANAK KASARE

SHELDON COOPER AND DOPPLER EFFECT

HISTORY OF DOPPLER EFFECTIn 1984 an Australian Physicist and mathematician, JC Doppler studied the behaviour of waves as the source, receiver or both are moving.He proposed as the source is moving the waves at the front have a higher frequency compared to the source being stationary. Also the waves trilling behind the source have a lower frequency compared to the source being stationary.The variation in frequencies is noticed by human ears as the change in pitch as the source moves.

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DOPPELR EFFECT

All waves travel outwards from the source (propagate). Stationary sources have waves moving outwards in a circular pattern. Moving source: waves ahead of the source are bunched closer. waves trailing behind the source are spread out. This is heard as a: high pitched sound at the front of the source and a distant drop in pitch as the moving source passes by.

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MOVING SOURCE APPROACHING A STATIONARY RECEIVER The Doppler Effect for a person throwing a ball at constant velocity every second and traveling at 1 m.s-1 towards the wall.

To understand what happens, consider the following analogy. Someone throws one ball every second at a man. Assume that balls travel with constant velocity. If the thrower is stationary, the man will receive one ball every second. However, if the thrower is moving towards the man, he will receive balls more frequently because the balls will be less spaced out. The inverse is true if the thrower is moving away from the man. So it is actually the wavelength which is affected; as a consequence, the received frequency is also affected. It may also be said that the velocity of the wave remains constant whereas wavelength changes; hence frequency also changes.5

CALCULATING THE OBSERVED FREQUENCY f- frequency observedf0- frequency emitted by the source c- is the velocity of waves in the mediumVr- is the velocity of the receiver relative to the medium.Vs- is the velocity of the source relative to the medium

SOURCE MOVING AT THE SPEED OF SOUND

The receiver in the front of the source will not receive any sound as all the sound waves are bunched at the source. f=c + 0c - c*f0()=c * f0 0=undefined

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SOURCE MOVING FASTER THEN THE SPEED OF SOUND

The receiver in the front of the source will not receive any sound waves As the waves are slower then the source and are trailing behind the source. f=c + 0c - 2c*f0()=c * f0 -c=Negative frequency

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SOURCE MOVING FASTER THEN THE SPEED OF SOUND

The receiver behind the source will hear the sound waves emitted from the source. This source radiates 2 waves: a pressure wave (Mach wave) and sound wave. These waves combine to create the shockwaves (sonic boom).The intensity of the boom increases as the speed of the source increases.

The region in which someone can hear the boom is called the boom carpet.

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Mark wavesAircraft moving faster then the speed of sound and creating 2 pressure waves; at the head (point of pressure rise) and the tail (point of sudden drop in pressure).

BIBLIOGRAPHY "What Happens When an Aircraft Breaks the Sound Barrier?" Scientific Americans. Scientific American, a Division of Nature America, Inc., 11 Mar. 2002. Web. 5 Oct. 2015. . Kaouri, Katerina. "The Sonic Boom Problem." YouTube. YouTube, 10 Feb. 2015. Web. 05 Oct. 2015. . "6.3 The Doppler Effect." Physics Uconn. Web. 5 Oct. 2015. ."Doppler Effect." The for Sound. Hyperphysic. Web. 05 Oct. 2015. . "Breaking the Sound Barrier with an Aircraft." The Sound. Hyperphysics. Web. . UNSW. "The Doppler Effect - A Multimedia Presentation from Physclips." The Doppler Effect - A Multimedia Presentation from Physclips. School of Physics UNSW. Web. 05 Oct. 2015. .