Imagine a bug

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

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

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 ↓

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

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

The Doppler effect causes the changing pitch of a siren

In front of the car… the pitch ↑

Behind the car… the pitch ↓

Note: The change in loudness is not the Doppler Effect! It is the shift in frequency!

http://www.youtube.com/watch?v=Y5KaeCZ_AaY

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

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.

http://www.youtube.com/watch?v=Y5KaeCZ_AaY

Named after Christian Doppler (Austrian) 1803-1853

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.

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).