Spectrum Targets

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Spectrum Targets

• Define the three types of spectra and explain how
  each type forms.

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Kinds of Visible Spectra Continuous Spectrum
unbroken band of colors which shows that its
source is sending out light of all visible
wavelengths. Bright-line Spectrum The bright
lines show that the source is emitting light in
certain wavelengths only. Dark-line Spectrum
The dark lines are in exactly the same place as
the bright lines from the same element in the
bright-line spectrum.
Bright-line spectrum of hydrogen
Dark-line spectrum of hydrogen
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• A continuous spectrum is produced by a hot solid,
  liquid, or dense gas.
• When a cloud of gas is in front of this hot
  source, an absorption spectrum is produced.
• A cloud of gas without a hot source behind it
  will produce an emission spectrum.

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Galaxies

• ES Ch. 31

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Targets

• Describe the size and parts of the Milky Way
  galaxy.
• Describe the shapes of galaxies.

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Galaxies
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Galaxies
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Galaxies

• The disk-like galaxies with spiral arms are
  called spiral galaxies and are divided into two
  subclasses normal spirals (S) and barred spirals
  (SB).

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Galaxies

• Elliptical galaxies are not flattened into disks,
  do not have spiral arms, and are denoted E.
• Others are irregular have no distinct shapes

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Galaxies
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Targets

• Explain the Doppler Effect and how it applies to
  astronomy.
• Define and explain a Red Shift and a Blue Shift.

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Doppler Effect

• Occurs when the source of waves moves
• Causes frequency to change
• Car moves toward you
• Sound waves compressed
• Higher frequency, Shorter wavelength
• Car moves away from you
• Sound waves stretched out
• Lower frequency, Longer wavelength

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Doppler Effect (Shift)

• http//www.colorado.edu/physics/2000/applets/doppl
  er.html

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Expanding Universe

• Doppler Effect occurs with electromagnetic waves
  (visible light, X rays, microwaves)

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Doppler Effect / Red Shift

• As object moves away, waves are stretched
  longer wavelength lower frequency.
• Red shift Bright line spectrum of elements
  moves towards the red end of spectrum
• http//lectureonline.cl.msu.edu/mmp/applist/doppl
  er/d.htm

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Doppler Effect / Red Shift
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Doppler Effect (Shift)

• Objects moving away are red-shifted objects
  moving closer are blue-shifted.
• Blue Shift Objects moving toward earth
• Light waves it emits are compressed
• Shifts toward violet (blue) end of spectrum
• Shorter wavelengths, higher frequencies

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Doppler Effect (Shift)

• When studying Sirius the spectral lines are
  shifted toward the red end of the visible
  spectrum
• Is Sirius moving closer or away from earth?
• Away

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Red Shift

• If ALL galaxies are red-shifted when viewed from
  Earth, what does this tell us about the universe?
• It is expanding in ALL directions