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Reflection

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					                 Reflection
• The law of reflection
  states that the angle
  of incidence is equal
  to the angle of
  reflection.
• All angles are taken
  from the normal line
  not the surface!
           Regular Reflection
• If all the normal lines
  are parallel to each
  other you get a
  precise image.
Reflection
             The image of a reflection
             is virtual, erect, and
             backwards.
Why is the front of an ambulance
      written backwards?
  Convex and Concave Images
• A convex mirror will
  give you a upright
  virtual and smaller
  image.
• A concave mirror will
  give you a real
  inverted image if you
  are beyond it focal
  point.
           Diffuse Reflection
• In Diffuse reflection
  you are not able to
  see a clear image
  because the normal
  lines are not parallel
  to each other.
  Example: white paper
  light is reflected but
  not like a mirror.
                    Refraction
• The bending of a wave as wave enters a new
  medium.
• A medium is what the wave is in. ie. Water, air,
  metal…
• n1 sinθ1 = n2 sin θ2
        n = index of refraction
• The index of refraction is a ratio to the
  speed of light in a vacuum vs. speed of
  light in a substance. I like to think of it as
  optical density!
• Air is 1.00
• Water is 1.33
• Lucite is 1.5
• Diamond is 2.42
    Calculate the speed of light in a
              substance.
•   n = c/v
•   c is speed of light (3.0 x 108 m/s)
•   Find the speed of light in water.
•   n = c/v
•   1.33 = (3.0 x 108 m/s) / v
•   v = 2.256 x 108 m/s
                               Diagram of refraction of water waves.
                               The source wave is encountering an
The straw seems to be          area of decreased water depth.
broken, due to refraction of
                               Notice how the bottom of the wave is
light as it emerges into the
                               moving slower than the top.
air.
                               Hence, you notice the bend.
                Refraction
• As a wave enters a
  new medium with a
  larger index of
  refraction the wave
  slows down, the angle
  decreases and the
  wavelength gets
  smaller.
• The frequency of the
  wave does not
  change!
               Internal Reflection
• Sinθc = 1/n
• The critical angle is the
  angle of incidence where
  it causes the light to be
  reflected at 90 degree to
  the normal . If the angle
  of incidence is greater
  than the critical angle
  you get total internal
  reflection. ie. fiber optics.

				
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posted:8/9/2011
language:English
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