Red Shift/Blue Shift The Doppler Effect with Light

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Red Shift/Blue ShiftThe Doppler Effect with Light
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Scientists Say

• The universe started like this
• Here we look at some java applets
• 2D big bang
• 3D big bang
• Today were going to learn why.

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Electromagnetic Spectrum
In which direction does the wavelength increase?
In which direction does the frequency increase?
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Stationary Wave Sources
L
R
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?
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Moving Wave Sources
L
R
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?
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Red Shift / Blue Shift, Notes
L
R

• Wave source approaching (blue shift)
• wave fronts are squished together
• wavelength is shorter, frequency is higher
• so it appears bluer

• Wave source moving away (red shift)
• wave fronts are spread apart
• wavelength is longer, frequency is lower
• so it appears redder

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What Color Does Ashley See?
What Color Does Jessica See?
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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.
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Draw What Youll SeeLabel the colors of the
light bulbs!
green ??
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?
? ? blue
red ? ?
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Green ? Yellow
Blue ? Green
Red ?Infrared
You Would See
Note Human Eyes Cant See Infrared
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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).

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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
This is the absorption spectrum (pattern of black
lines) from a close star like our sun.
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
If the nearby galaxy wasnt moving, the
absorption spectrum (the pattern of black lines)
would be in the same place.
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
Is the pattern red shifted or blue shifted?
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
The pattern is red shifted since it is shifted
towards the red side of the spectrum.
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
The pattern is red shifted.
So Is the nearby galaxy moving towards us or
away from us?
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
The pattern is red shifted.
So Is the nearby galaxy moving towards us or
away from us?
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
The bigger the shift, the faster the light source
is moving.
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
Which is moving away faster the nearby galaxy or
the faraway galaxy?
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
Which is moving away faster the nearby galaxy or
the faraway galaxy?
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What We See
Close Star Nearby Galaxy Faraway
Galaxy Really Faraway Galaxy
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Your Turn
The further away a galaxy is, the bigger the
______ shift. So far away galaxies are moving
away _______.
red
blue
faster
slower
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Your Turn
The further away a galaxy is, the bigger the
______ shift. So far away galaxies are moving
away _______.
red
red
blue
slower
faster
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Your Turn
The further away a galaxy is, the bigger the
______ shift. So far away galaxies are moving
away _______.
red
red
blue
faster
slower
faster
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Scientists Conclusions

• 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.
• Thats why the fastest galaxies are the furthest
  away.