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DOPPLER EFFECT. The observed frequency of a wave changes when there is relative motion between the source of the wave and the observer. Sonic Doppler Effect. Stationary Source. Moving Source. higher frequency. lower freq. higher freq. lower freq. Source moving towards observer
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DOPPLER EFFECT The observed frequency of a wave changes when there is relative motion between the source of the wave and the observer.
Stationary Source Moving Source higher frequency lower freq.
higher freq. lower freq.
Source moving towards observer higher pitch Source moving away from observer lower pitch
Doppler Formulas motion towards: v + vo f’ = f -------- v - vs motion away: v - vo f’ = f -------- v + vs f’ = observed freq. f = emitted freq. v = wave speed vo = observer speed vs = source speed
A train moving at 20 m/s sounds its 200 Hz horn. The speed of the sound is 340 m/s. Observed frequency when moving into station and moving out of station? 189 Hz 213 Hz
Speed of car calculated from emitted and observed frequencies of radar waves
If source of wave moves as fast (or faster) than the wave. Mach 1
Sudden change in pressure heard as explosion when plane passes overhead.
Other examples of shock waves: supersonic bullet tip of whip
Astronomy Application of Doppler Light from distant galaxies is of a lower frequency (red-shifted) Conclusion: galaxies all moving away; universe is expanding