The Doppler EffectThe Doppler Effect

Doppler Effect & Doppler Effect & SoundSound Christian Doppler Observing the D

oppler Effect Discuss what you hear with your Discuss what you hear with your

partnerpartner

The Doppler EffectThe Doppler Effect

Applies to anything that produces Applies to anything that produces waveswaves– SoundSound– LightLight

Stationary SourceStationary Source

the sound waves are spread out the sound waves are spread out evenlyevenly

everyone everyone

experiences experiences

the same the same

waveswaves

Source in MotionSource in Motion

Waves will be Waves will be – compressed in front of the source compressed in front of the source

(shorter wavelengths)(shorter wavelengths)– spread out behind the source spread out behind the source

(longer wavelengths)(longer wavelengths)

Breaking the Sound Breaking the Sound BarrierBarrierMach 1Mach 1 Object moves just Object moves just

barely faster than the barely faster than the speed of soundspeed of sound

SupersonicSupersonic Source is moving Source is moving

faster than the sound faster than the sound waves it createswaves it creates

The sound source will The sound source will pass by a stationary pass by a stationary observer before the observer before the observer actually observer actually hears the sound it hears the sound it createscreates

Doppler Effect & Light Doppler Effect & Light WavesWaves What happens to light waves whe

n a star moves?

Doppler Effect & Light Doppler Effect & Light WavesWaves In front of source (star)In front of source (star)

– Light waves are compressed Light waves are compressed – Wavelengths are made shorter as Wavelengths are made shorter as

the spectral lines are shifted toward the spectral lines are shifted toward blue end of the spectrumblue end of the spectrum

– Called Called Blue shiftBlue shift

Blue ShiftBlue Shift

Doppler Effect & Light Doppler Effect & Light WavesWaves Behind the source (star)Behind the source (star)

– Light waves are spread outLight waves are spread out– Wavelengths are made longer as the Wavelengths are made longer as the

spectral lines are shifted toward red spectral lines are shifted toward red end of the spectrumend of the spectrum

– Called Called Red shiftRed shift

Red ShiftRed Shift

Moving away from you