Total Internal Reflection

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Total Internal Reflection
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Critical Angle

• Critical Angle (ltc) The term used to describe
  an angle of incidence that produces an angle of
  refraction of 90o.
• When the angle of refraction reaches 90o, the
  refracted ray will lie along the boundary between
  two media (such as water and air).

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Total Internal Reflection

• Total Internal Reflection When the angle of
  incidence is larger than the critical angle,
  there is no refraction from one medium to
  another. All of the light is reflected back to
  the first medium.
• Only occurs when light travels from a medium in
  which the speed of light is lower to a medium in
  which the speed of light is higher.

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Phenomenon of Total Internal Reflection
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Binoculars and Total Internal Reflection

• Binoculars consist of three main parts
• Convex Lenses To magnify the image.
• Eyepiece Brings the image into focus and makes
  it visible to the eye.
• Two Prisms The prisms used for binoculars are
  shaped like isosceles right triangles, which
  changes the direction of the light ray by 90o.

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How Prisms Work in Binoculars

• Light first enters perpendicular to one of the
  short sides, producing an angle of incidence of
  zero. Thus, no refraction at this surface occurs
  and it goes straight through to hit the long
  side.
• At the long side, the both the angle of incidence
  and reflection is 45o, changing the direction of
  the light by 90o each time. Thus, the total
  change in direction is 180o.

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How Prisms Work in Binoculars
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Optical Fibers and Total Internal Reflection

• Optical fibers are long, thin strands of very
  pure glass that are arranged in bundles called
  optical cables and used to transmit light signals
  over long distances.
• Parts of an Optical Fiber
• Core - Thin glass center of the fiber where the
  light travels.
• Cladding - Outer optical material surrounding the
  core that reflects the light back into the core.
  The cladding must have a lower index of
  refraction than the core.
• Buffer coating - Plastic coating that protects
  the fiber from damage and moisture.

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Optical Fibers and Total Internal Reflection

• Hundreds or thousands of optical fibers are
  arranged in bundles to make up optical cables.
• When light enters the fiber and hits the boundary
  between the core and the cladding at an angle
  larger than the critical angle, total internal
  reflection occurs along the entire fiber until it
  reaches the end.