What is the What is the DOPPLERDOPPLER EFFECT? EFFECT?

Doppler and SoundDoppler and Sound When sound waves are made they spread When sound waves are made they spread

out evenly in all directions like ripples on a out evenly in all directions like ripples on a pool of waterpool of water

A stationary train sounds the same from all A stationary train sounds the same from all directions.directions.

When the train making the sound or the When the train making the sound or the listener are moving there is an apparent listener are moving there is an apparent change in frequency. change in frequency.

Higher frequency when moving towards Higher frequency when moving towards each other.each other.

Lower frequency when moving apart.Lower frequency when moving apart.

Doppler and LightDoppler and Light

The Doppler effect occurs with light waves The Doppler effect occurs with light waves and other energy wave types.and other energy wave types.

In the area of astronomy the Doppler In the area of astronomy the Doppler effect helps explain the effect helps explain the red shiftred shift in stellar in stellar objects.objects.

Red ShiftRed Shift Stars emit light in specific patterns called Stars emit light in specific patterns called

spectral lines.spectral lines. Stellar objects found outside of our galaxy all Stellar objects found outside of our galaxy all

had spectral lines that had shifted towards the had spectral lines that had shifted towards the red end of the spectrum. red end of the spectrum.

Red light has lower wave frequency Red light has lower wave frequency which means the objects are moving away which means the objects are moving away from the earth.from the earth.

Big BangBig Bang

The red shift shows The red shift shows every galaxy is every galaxy is moving away from the moving away from the Earth.Earth.

This supports the This supports the concept of an concept of an expanding universe . expanding universe . This in turn supports This in turn supports the Big Bang theory.the Big Bang theory.

LinksLinks

www.pbs.org/wnet/hawking/strange/html/untitled_14_stuff.htmlwww.pbs.org/wnet/hawking/strange/html/untitled_14_stuff.html

webphysics.davidson.edu/Applets/Doppler/Doppler.html

www.colorado.edu/physics/2000/applets/doppler.html

lectureonline.cl.msu.edu/~mmp/applist/doppler/d.htm www.colorado.edu/physics/2000/applets/doppler2.html