Red Shift/Blue Shift The Doppler Effect with Light.
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Transcript of Red Shift/Blue Shift The Doppler Effect with Light.
Red Shift/Blue ShiftThe Doppler Effect with Light
Scientists Say:
The universe started like this:
Here we look at some java applets:
2D big bang
3D big bang
Today we’re going to learn why.
Electromagnetic Spectrum
Increasing f
Increasing λIn which direction does the wavelength increase?
In which direction does the frequency increase?
Stationary Wave Sources
LR
Q: Does either eye (left or right) observe a different wavelength light?
A: No. Both eyes observe the same wavelength, yellow, light.
Q: Does either eye (left or right) observe a different wavelength light?
Moving Wave Sources
LR
Q: Does either eye (left or right) observe a different wavelength light?
A: Yes. The left eye will see longer wavelength light and the right eye will see shorter wavelength light.
Q: Does either eye (left or right) observe a different wavelength light?
Red Shift / Blue Shift, Notes:
L R
a.Wave source moving away (red shift)
i. wave fronts are spread apartii. wavelength is longer, frequency is loweriii. so it appears redder
b. Wave source approaching (blue shift)i. wave fronts are
squished togetherii. wavelength is shorter,
frequency is higheriii. so it appears bluer
Q: What happens to the light the right eye see?
Red Shift Blue Shift No Shift
Q: What happens to the light the left eye sees?
Red Shift Blue Shift No Shift
What Color Does Ashley See?
What Color Does Jessica See?
A Person Stands on a PlanetThe Planet is Flying Away
The person is holding a red and a blue light bulb. A green light bulb grows out of their head.
Draw What You’ll See:Label the colors of the light bulbs!
The person is holding a red and a blue light bulb. A green light bulb grows out of their
head. What colors will you see?
red ?
green ?
? blue
Red Infrared*
Green Yellow
Blue Green
You
Would
See
* Note: Human Eyes Can’t See Infrared
The Sun & The Stars
• The sun is a star.• The sun and the stars are all made out of
hydrogen.• Light from hydrogen leaves a distinctive
pattern of black lines (an absorption spectrum).
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
This is the absorption spectrum (pattern of black lines) from a close star like our sun.
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
If the nearby galaxy wasn’t moving, the absorption spectrum
(the pattern of black lines) would be in the same place.
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
Is the pattern red shifted or blue shifted?
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
The pattern is red shifted
since it is shifted towards the red side of the spectrum.
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
The pattern is red shifted.
— So —
Is the nearby galaxy moving towards us or away from us?
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
The pattern is red shifted.
— So —
Is the nearby galaxy moving towards us or away from us?
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
The bigger the shift, the faster the light source is moving.
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
Which is moving away faster:
the nearby galaxy or the faraway galaxy?
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
Which is moving away faster:
the nearby galaxy or the faraway galaxy?
What We See
CloseStar
Nearby Galaxy
Faraway Galaxy
Really Faraway Galaxy
fasterslower
The further away a galaxy is,
the bigger the ______ shift.
So far away galaxies are moving away _______.
Your Turn
red blue
red blue
The further away a galaxy is,
the bigger the ______ shift.
So far away galaxies are moving away _______.
Your Turn
slower faster
red
slower
red blue
The further away a galaxy is,
the bigger the ______ shift.
So far away galaxies are moving away _______.
Your Turn
faster
red
faster
The further away a galaxy is, the bigger the red shift.
So far away galaxies are moving away faster.
• The galaxies must have been close together in the past.
• A tremendous explosion (a big bang) must have made everything explode outward.
• That’s why the fastest galaxies are the furthest away.
Scientists’ Conclusions