Bending Light, Fiber Optics and Optical Phenomena in Nature

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Bending Light, Fiber Optics and Optical Phenomena
in Nature

• The double rainbow!!!

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Partial Reflection Refraction

• Sometimes when you look out a window you see
  outside and you see your reflection at the same
  time
• This depends on the angle of incidence as well as
  the relative indices of refraction of the two
  media.
• Consider air to water light traveling direction
  at the water (at 90º) will go straight through,
  however as the angle of incidence increase more
  light is reflected rather than passing straight
  through

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Scuba diving

• Because at large angle of incidence most of the
  light is reflected off the water when you are
  scuba diving light appears to be coming through a
  hole above you at the surface of the water

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Water and refraction

• Even though you know water is clear, you have
  difficulty seeing things farther away from you in
  the water.
• This is because when you look farther away you
  increase the angle of incidence which causes more
  reflection and blocks your view into the water.

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Critical angle Total Internal Reflection

• The angle of incidence that produces a refracted
  ray at an angle of 90º from the normal
• It has the symbol ltc
• When the angle of incidence is greater than ltc
  you get total internal reflection and all light
  is reflected back not passing through the medium.

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Changing the direction of light

• We can control light by putting the medium
  borders at large angles of incidence so that we
  get total reflection.
• Bike reflectors and optical fibers are examples-
  with bike reflectors light will always bounce
  back the way it came

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Fiber Optics
Total internal reflection occurs all the way
through the fibre so light travels quickly
--telecommunications uses fiber optic cable to
send information quickly --the medical field uses
fiber optics in two ways, one to light up the
area through endoscope (sending a tube into the
body) second it uses fiber optics to send back
images that the doctors can analyse. Non invasive
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Rainbows and double rainbows
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Sun dogs

• Similar to rainbows, but instead of water
  droplets it is ice crystals refracting sunlight.
• The most stunning sun dogs occur on cold clear
  mornings or evenings

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Apparent depth
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Shimmering and mirages

• Shimmering small scale
• Mirage-large scale
• Simmering is the apparent movement of objects in
  hot air over objects and surfaces
• Mirages are the bending of light rays passing
  through layers of air that have extremely
  different temperatures. Since you are used to
  thinking that light travels in a straight line
  you interpret the origin of the light being on
  the ground when it is really the sunlight being
  refracted upwards.

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Mirages
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Homework

• Case study Pg 472 and 473
• Pg 475 1-7