Reflection and Refraction

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Reflection and Refraction
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Total or Partial.

• Total-All of the energy of the wave is reflected,
  as a reflection off a mirror
• Partial-Some of the energy is transmitted, some
  reflected, as a reflection off of a window

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The Law of Reflection

• Incident rays and reflected rays make equal
  angles with a line perpendicular to the surface,
  called the NORMAL

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Mirrors

• Virtual Image- Image appears to be where no light
  rays could be forming it--plane mirrors ONLY make
  virtual images
• Real Image-Image appears at a place where light
  rays are actually forming the image--can be made
  by curved mirrors only

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Diffuse Reflection

• When light is incident on rough surface, and it
  is reflected in many directions

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Reflection of Sound

• Echoes-come from all surfaces in a room
• Study of echo properties is acoustics
• When many echoes combine, the result can be
  garbled--this is called reverberation
• Proper design eliminates reverberations and
  reflects sound evenly

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Refraction

• Waves bend when one part of the waves is made to
  travel more slowly or faster than another part
• Refraction of Sound--temperature of air can cause
  this
• Refraction of Light--when passing into a new
  medium

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Atmospheric Refraction

• Mirages--warm air acts as a different medium than
  cooler air

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Dispersion

• Separation of light into colors arranged
  according to their frequency

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The Rainbow

• Dispersion due to refraction in raindrops--noone
  sees the same rainbow as anyone else since it is
  refracting thru different droplets

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Total Internal Reflection

• Submerge a flashlight in a bathtub in a dark
  room--no light gets out if the angle is greater
  than critical

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Optical Fibers

• Optical fibers--light stays in since the angle is
  always greater than critical

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Lenses
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Converging and Diverging Lenses

• Converging brings light rays together
• Diverging spreads out light rays
• Type of lens depends on the medium involved

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Image Formation In Lenses

• Converging Lenses

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Image Formation In Lenses

• Divergent lenses

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Common Optical Instruments

• Camera

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Common Optical Instruments

• Telescope

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Common Optical Instruments

• Compound microscope

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The Eye

• Works by refraction thru a shapeable lens
• Defects caused by shape of eye or distortion of
  lens or cornea
• Hypermetropia-farsight
• Myopia-nearsight
• Astigmatism-cornea not even
• Presbyopia-lens loses ability to change shape
  quickly

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Defects of Lenses

• Abberations--refraction causes fuzzy image
• Spherical aberration-bad grinding causes focus at
  different places--fix by combining lenses
• Chromatic aberration-colors refract
  differently--correct with achromatic lenses

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Homework!!
Complete Take-home Worksheet