10.2 Producing Visible Light

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10.2 Producing Visible Light
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Sources of Light

• Natural light Artificial light
• -produced by sun -produced human through or
  stars technology

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Incandescent light sources

• Light produced by an object that was heated
• Ex. Incandescent light bulb
• -electricity heats a metal filament called
• tungsten which produces light

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Luminescent light

• Light is releases by an object that has NOT been
  heated
• There are several types of luminescent light
• -Fluorescent -triboluminescence
• -phosphorescent -electric discharge
• -chemiluminescent -bioluminescence

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Fluorescent Light

• -light is emitted by an object when it is
  exposed to ultraviolet radiation
• Ex. Fluorescent light bulbs are coated with a
  white powder called a phosphor and contain a
  small amount of gas. The phosphor will glow
  after being exposed to energized particles
  (electricity energized the gas)

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Phosphorescent light

• A substance that can store energy from radiation
  will emit light slowly over a long period of time
• Glow in the dark after being energized by light
• Ex. Glow in the dark paint

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Chemiluminescent

• Light is produced from a chemical reaction
  without a rise in temperature
• Light produced is called cool light
• Ex. Glow in the dark sticks

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Bioluminescence

• Special kind of chemiluminescence
• A plant or animal produces light

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Triboluminescence

• Light is produced by friction
• Some crystals glow by rubbing them together
• Ex. quartz

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Electric Discharge

• Electric current is passed through the air or
  another gas
• Ex. Neon signs
• carbon arc light

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Light Emitting Diode (LED)

• Electrical energy is transformed directly into
  light energy (electroluminescence)
• Consume less energy than fluorescent/incandescent
  devices and last longer
• LEDs are made out of semiconductors (can change
  how well it conducts electricity) they emit
  light when electricity is passed through it.

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Homework

• P. 395 1-5
• P. 398 1-5