The Doppler Effect

The Doppler Effect 

The Doppler Effect Description 

When an ambulance or Police car with the sirens on passes by you, there is a notice drop in pitch. The unusual sounds created drop by this passing by ambulance is part of the Doppler Effect. The Doppler Effect is produced by a source of waves or the observer that is in motion. When a moving source of waves is approaching the observer there is an apparent upwards shift of frequency, and conversely when a moving source of waves is leaving there is an apparent downward shift in frequency. This apparent change of frequency is NOT due to a change of frequency given by the source of waves. The frequency just appears greater or lesser because of the distance between the observer and source of waves is increasing or decreasing. 

The Doppler effect does not just apply to sound wave. The Doppler Effect applies to all types of waves including light waves, water waves, electromagnetic waves, sound waves, and many others. 

The Doppler Effect in Space

The Doppler Effect is often study by astronomers to determine information on distant starts and galaxies. Astronomers used the shift in frequency of electromagnetic waves to acquire more information about these distant galaxies and stars. Stars that have a upward shift in frequency are classified as have blue shift, and are known to be rotating in a direction toward Earth.  Stars that have a downward shift in frequency are classified as have red shift, and are known to be rotating in a direction away from Earth. The Doppler is partly responsible for the belief that that universe is expanding. The emission of frequcney given off by distant stars and galaxies, using the information know by the Doppler Effect, supports the theory of universal expansion. 

By: Rachel Wade