Refraction, Lenses,

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Refraction, Lenses, Sight
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Refraction

• The change in direction of a wave as is crosses
  the boundary between two media in which the wave
  travels at different speeds.

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Index of Refraction
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Snells Law
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Index of Refraction
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Dispersion

• The separation of light into colors arranged
  according to their frequency, by interaction with
  a prism or diffraction grating.

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Rainbows

• White light separates into different colors
  (wavelengths) on entering the raindrop because
  red light is refracted by a lesser angle than
  blue light. On leaving the raindrop, the red rays
  have turned through a smaller angle than the blue
  rays, producing a rainbow.

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Lenses
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Converging Lens
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Rules For Converging Lenses

1. Any incident ray traveling parallel to the
   principal axis of a converging lens will refract
   through the lens and travel through the focal
   point on the opposite side of the lens.
2. Any incident ray traveling through the focal
   point on the way to the lens will refract through
   the lens and travel parallel to the principal
   axis.
3. An incident ray which passes through the center
   of the lens will in effect continue in the same
   direction that it had when it entered the lens.

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Image Formation by Converging Lens
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Diverging Lens
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Rules For Diverging Lenses

1. Any incident ray traveling parallel to the
   principal axis of a diverging lens will refract
   through the lens and travel in line with the
   focal point (i.e., in a direction such that its
   extension will pass through the focal point).
2. Any incident ray traveling towards the focal
   point on the way to the lens will refract through
   the lens and travel parallel to the principal
   axis.
3. An incident ray which passes through the center
   of the lens will in effect continue in the same
   direction that it had when it entered the lens.

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Diverging Lens Image Formation
Always Virtual, Smaller, and Right-Side Up
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The Human Eye
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The Human Eye
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Normal Eye Focus
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Near-Sighted (Myopia)
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Far-Sighted (Hypermetropia)
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Astigmatism

• Cornea is oval shaped instead of spherical. This
  causes light to focus on two or more spots.

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LASIK

• Laser-assisted In Situ Keratomileusis