Visible Light and how light waves interact with mediums

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Visible Light
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Visible Light used in many ways

• Vision
• Find food and other survival activities
• Plants need it to make their food
• Can you think of anything else?

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Where does it come from?

• Most of it comes from the sun
• The production of light by materials at high
  temperatures is called incandescence
• Other sources include Lightening and Fire

4
Living things produce light

• Luminescence is the production of light without
  the high temperatures needed for incandescence.
• The production of light by living organisms is
  called bioluminescence.
• Produce by chemical reactions and not intense
  heat
• Insects, worms, fish, squid, jellyfish, bacteria,
  and fungi

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LEDs

• Light-emitting diodes
• Idea came from the bioluminescence of animals
• Light that produces little heat and uses almost
  all of its electrical energy to make light
  instead of the thermal energy

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Human produced visible light

• First was fire
• Electrical lighting in late 1800s (used
  tungsten) was known as incandescent bulbs because
  they used high temps
• 1980shalogen bulbs use gas to combine with
  tungsten atoms which causes them to last longer
• Fluorescence bulbs absorb EM radiation of one
  wavelength and give off EM radiation of another.
  Filled with mercury vapor and other gases that
  give off ultraviolet light

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Other artificial light

• Use gas instead of a filament
• Neon lights (diff gases produce diff colors)
• Vapor lights (sodium)
• LEDs uses a semiconductor that regulates
  electric current to produce light
• Used little energy
• Last longer
• Brighter light
• Not easily broken