Transcript The Doppler Shift

The Doppler Shift
The Visible Spectrum
White light splits into the colors of the rainbow
when passed through a prism.
The Visible Spectrum
Red Orange Yellow Green Blue Indigo Violet
The Visible Spectrum
R
O
Y
G
B
I
V
I would like to introduce...
RO Y
G
BIV
Sometimes it gets reversed...
RO Y
G
BIV
Sometimes it gets reversed...
RO Y
G
BIV
Sometimes it gets reversed...
VI B
G
YOR
(Roy’s evil twin brother.)
But the order makes no difference.
There’s more to the spectrum
than what you can see.
Ultraviolet
(UV)
There’s more to the spectrum
than what you can see.
Pure White Light
Glowing Gas
The “fingerprint” of an
element.
Neon Light
Glowing Gas
Hydrogen Light
When sound is made by a stationary
object, you hear a certain
frequency...
Insert constant sound here
If you could see it, it would
look like this...
But when the sound moves towards
you, it sounds higher in pitch.
Waves get compressed.
The faster the object moves, the
higher the pitch.
Waves get compressed more.
When the object moves at the speed
of sound, the waves overlap...
...and you get a sonic boom.
Fly faster than sound, and you’re
gone before the boom is heard.
Fly faster than sound, and you’re
gone before the boom is heard.
Fly faster than sound, and you’re
gone before the boom is heard.
An on-line visualization:
• http://www.phy.ntnu.edu.tw/java/Doppler
/Doppler.html
When the sound moves away, it
sounds lower.
Waves are stretched.
What it Sounds Like.
Car 1
Deep Jet
Mortor
Bike 1
Prop2
Prop2
Prop 1
Race1
Race1
Whine Jet 1
Race2
Race2
The same shifting happens with the
light from a moving star.
Lower Frequency
Higher Frequency
The spectrum of hydrogen that is
from a stationary source.
When the star is moving
closer...
Stationary Hydrogen
“Blue Shifted” Hydrogen from star
moving towards Earth.
And when a star moves away
from us...
Stationary Hydrogen
Lines are shifted to the red end.
And when a star moves away from
Faster
us...
Stationary Hydrogen
Lines are shifted farther to the red end.
Since the universe is
expanding...
• All distant objects have a red shift.
• The farther the object, the more extreme the red shift.
Astronomers use this relationship
between distance and speed to measure
the distance to distant stars and galaxies.