Total internal reflection and other applications of refraction

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Total internal reflection and other applications
of refraction
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TOTAL INTERNAL REFLECTION
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Total internal reflection

• When light moves from a dense material to less
  dense material, light bends away from normal, ?r
  is greater than ?i
• If light comes into the boundary at a large
  enough angle, ?r becomes gt 90, no longer
  refracts, reflects

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Total internal reflection
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The critical angle

• The angle that there is no more refraction from
  the incoming light
• Where ?r 90
• To find the critical angle use snells law

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Total internal reflecttion
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Total Internal reflection occurs

• When light moves from a more dense medium to a
  less dense medium
• ?i gt ?c
• Light will bounce away from boundary to angle
  of incidence

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To recap

• When light travel from more dense to less dense
  medium
• If ?i lt ?c, light refracts (use Snells law to
  calculate angles
• If ?i ?c, light moves along the boundary
• If ?i gt ?c, light reflects

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Book Homework

• Pg 510, 76, 77, 80
• Pg 877, 1-3

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REAL LIFE APPLICATIONS OF TOTAL INTERNAL
REFLECTION
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The sparkle of Diamonds

• Light enters the diamond
• The sides of a diamond have be cut in such a way
  as to cause total internal reflection for most
  light and have it bounce towards the top of the
  diamond
• Concentrated light leaves the top of diamond

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Diamond and total internal reflection
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Fiber optics
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FIBER OPTICS
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MIRAGES
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Mirages

• Why do you see water on the road in the summer?

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Mirages
                                                                                  

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Mirage
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Mirage
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Requirements for a mirage

• Long flat surface
• Lots of sunlight
• The air close to the surface to be warmer than
  air father above

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Mirages

• Light passes from denser colder air to warmer
  less dense air
• Eventually angle of incoming light passes through
  critical angle.
• Starts to reflect
• Your eye takes in light, extends back to ground

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DISPERSION OF LIGHT
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Prisms and the dispersion of light

• Speed of light is determined by the interaction
  between light and the atoms that make up the
  medium it passes through
• Different colors of light move at different
  speeds, refract at different angles

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Dispersion

• White light will be spread out into its different
  colors as it passes into an optically dense
  material
• Different wavelengths result in different
  frequencies, causes different reactions
• Greater changes in direction result from higher
  index of refraction

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Dispersion facts

• Each wavelength will interact slight different as
  it passes into a transparent object
• Causing sunlight to break into different colors
  as it passes through a prism
• Red light changes the least, violet changes the
  most (remember why the sky is blue)

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Understand Pink Floyd through physics!
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RAINBOWS
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Reguirements for generating a rainbow

• Rain clouds in a distance in front of you
• Sun behind you

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Rainbows

• Result from light being both dispersed and total
  internal reflected as it enters water drops in
  the air
• Pg 491-492

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