Transcript The Doppler Effect

The Doppler Effect
Moving stars and changing colors
Waves from a Moving Source
When a source of waves moves relative to an
observer the frequency observed is affected.
As it approaches wavelength is shortened and
frequency is higher
As it leaves wavelength is lengthened and frequency is
lowered.
Blue and Red Shifts
For light this means the colors change…
If the star is approaching colors are shifted to the
Blue
If moving away they are shifted to the Red.
Blue and Red Shifts are seen by looking for the
pattern of the
absorption
lines.
If the pattern
of lines
appear to
move.
There has
been
a shift
How much it is shifted tells you how fast it
is moving away or toward you.
More shift = faster
So if the 656 nm line is shifted to 750 nm
that star is moving away faster than if the
shift was to 700 nm.
Radial Velocity is found by the Doppler
effect.
Radial Velocity is how fast an object is
moving toward or away.
An object moving in a circle around the
observer would have a radial velocity of…
Zero!
And will have No Blue or Red Shift!