Light

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Light
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Early ideas about Light

• Some Greeks thought light came from the eyes.
• Particle Theory of Light Newton
• Wave Theory of Light Huygens
• Electromagnetic Theory Maxwell
• Back to the particle model Einstein
• Dual nature particles and waves

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Speed of Light

• Galileo experiment with lanterns
• Olaus Roemer and Jupiter
• Albert Michelson and spinning mirror
• 8 minutes for light to travel from the sun to
  Earth
• Distance light travels in one year is called a
  light-year

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Electromagnetic Waves

• Light is energy that is emitted by accelerating
  electric charges
• Produces electric and magnetic waves
• Electromagnetic waves are distinguished by their
  different frequencies and wavelengths

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Electromagnetic Spectrum
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Reflection

• When any wave reaches a boundary, some of the
  wave bounces back (and some is transmitted to the
  next medium)
• Holding a slinky
• This is reflection

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Law of Reflection

• Angle of incoming light ray
• angle of reflected light ray
• q q
• qi qr

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