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Imagine a bug jiggling its legs and bobbing up and down in the middle of a quiet puddle.

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Presentation on theme: "Imagine a bug jiggling its legs and bobbing up and down in the middle of a quiet puddle."— Presentation transcript:

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3 Imagine a bug jiggling its legs and bobbing up and down in the middle of a quiet puddle

4 What would happen to the waves if the bug began to swim forward, toward B?

5 What does that do to the frequency of the waves, in front of the bug and behind the bug? In front of the bug…the frequency ↑ Behind the bug…the frequency ↓

6  http://www.fearofphysics.com/cgi- bin/doppler.cgi?dir=t&vs=200&mode=wrap http://www.fearofphysics.com/cgi- bin/doppler.cgi?dir=t&vs=200&mode=wrap

7 Pitch…. A man’s vocal chords vibrate slower than a woman’s…hence a lower voice=lower pitch

8 The Doppler effect causes the changing pitch of a siren In front of the car… the pitch ↑ Behind the car… the pitch ↓

9 Note: The change in loudness is not the Doppler Effect! It is the shift in frequency!  http://www.youtube. com/watch?v=Y5Kae CZ_AaY http://www.youtube. com/watch?v=Y5Kae CZ_AaY

10 Police use the Doppler effect of radar waves to measure the speeds of cars on the highway

11 2011, Aroldis Chapman reached back and threw a pitch to Andrew McCutchen of the Pirates. The pitch wound up being high and tight, not a location necessarily to be proud of, and yet he received a standing ovation. Why the standing ovation, you may ask? The stadium radar reading displayed a velocity of 106 MPH, a speed that has only been topped twice since baseball started recording pitch velocities.Pirates

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13  http://www.youtube.com/watch?v=Y5KaeCZ _AaY http://www.youtube.com/watch?v=Y5KaeCZ _AaY

14  Named after Christian Doppler (Austrian) 1803-1853

15 When a source moves toward you, do you measure an increase or decrease in wave speed? Neither! It is the frequency of a wave that undergoes a change, not the wave speed.

16 How does the apparent frequency of waves change as a wave source moves?  The sound waves become more frequent (compressed together).  The sound waves become less frequent (stretched apart).


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