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Doppler Effect
Doppler Effect Heard
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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?
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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 blueshifted or red-shifted, because blue and red are
respectively near the frequency of high and low
ends of the visible spectrum.
Doppler Effect Seen
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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
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The Doppler Effect causes the absorption
spectrum of a star to shift toward the red or
blue.
Redshift
Blueshift