Doppler Effect

Doppler Effect Heard Everyone remembers what it sounds like when a police car comes closer to you and then passes by. The sound changes from a higher pitch to a lower pitch. Example This change in sound is an example of what is called the Doppler Effect

What Is The Doppler Effect? When the source of some wave (eg. Sound, light, etc.) is approaching you, the wave you received will be in a higher frequency (shorter wavelength) compared to the case when the source is stationary. If the source is leaving you, you will see lower frequency wave (longer wavelength). This is called the Doppler effect. In astronomy, we will call the EM wave blue-shifted or red-shifted, because blue and red are respectively near the frequency of high and low ends of the visible spectrum.

Doppler Effect Seen When a source of light (like a star) is stationary, the wavelengths of light remain the same distance apart. When a source of light is moving toward you, the wavelengths of light get closer together. This is called blueshift. When a source of light is moving away from you, the wavelengths of light get farther apart. This is called redshift. This is how scientists find out if the universe is growing, shrinking, or staying the same size

Spectrum Shift The Doppler Effect causes the absorption spectrum of a star to shift toward the red or blue.

Redshift Blueshift