Warmup:

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Warm-up

• List the regions of the EM spectrum from the
  greatest energy to the least.
• What color of visible light has the greatest
  energy?
• What color of visible light has the greatest
  wavelength?

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Visible Light COLOR

• What makes a pumpkin orange?
• The pumpkin has chemicals in its skin that
  absorb all the colors except orange. Even though
  all the colors are hitting the pumpkin, it only
  emits the orange light, so thats what we see.
• White light is the presence of all colors.
• white objects reflect all colors
• Black is the absence of all colors.
• black objects absorb all colors (reflect none)

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Visible Light COLOR

• In order to understand light and color, we need a
  quick understanding of atomic structure

Nucleus (positive)
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Visible Light COLOR

• In order to understand light and color, we need a
  quick understanding of atomic structure

Electron orbitals (negative)
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Visible Light COLOR
Ground state the lowest-energy orbit of an
electron (the happy place)
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
Excitation when the electron receives energy
and jumps to a higher-energy orbit
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Visible Light COLOR
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Visible Light COLOR
De-excitation when the electron falls back to
its ground state
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Visible Light COLOR
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Visible Light COLOR
Emitted photon of visible light
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
The electron makes a bigger jump because green
has more energy than orange.
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
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Visible Light COLOR
This atom can only emit orange and green light,
because those are the only two jumps that this
electron can make. This is determined by the
spacing of the orbitals.
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Visible Light COLOR

• Each element has its own unique set of orbital
  spacings, so each element also has its own set of
  colors.
• The unique set of colors for each element is sort
  of like a fingerprint for that element.
• We can see the set of colors for each element
  when we look at the emission spectrum for that
  element.
• We take an element in gas form, run electricity
  through it to make it glow, then pass the light
  through a prism to look at the colors.

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Visible Light COLOR

• Another way to identify an element is using an
  absorption spectra.
• In this case, we pass white light through an
  element gas, and all the colors pass through
  except for the characteristic colors of the
  element.
• This is how we have discovered that there is iron
  in the gas that surrounds the sun.

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Visible Light COLOR

• Other types of light emission
• Incandescence light emission due to high
  temperature
• Excited solids (like Tungsten and even firewood)
  emit all visible frequencies
• Fluorescence absorbing radiation of a high
  frequency and emitting at a lower frequency
• When something seems unnaturally bright, it is
  probably absorbing UV (invisible) photons, but
  emitting the light as visible light. This is
  called fluorescing. This is seen in NEON
  objects.

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Visible Light COLOR

• Phosphorescence emission (or de-excitation)
  occurs after a time delay
• Examples Glow-in-the-dark products, and
  certain types of plankton that can be seen
  glowing in the water at night.

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Visible Light COLOR

• Polarization of Light
• When light travels, the electric fields vibrate
  in all directions
• We can polarize light, meaning we can only
  allow it to vibrate in one direction.
• Sunglasses use this technique to improve your
  vision in some conditions (skiing, fishing, etc)