Ray Approximation

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Ray Approximation
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Specular Reflection
(from a smooth surface)
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Diffuse Reflection
( rough surface, not considered in this
class )
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Reflection

• The normal is a line perpendicular to the surface
• It is at the point where the incident ray strikes
  the surface
• The incident ray makes an angle of ?1 with the
  normal
• The reflected ray makes an angle of ?1 with the
  normal

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Law of Reflection

• The angle of reflection equals angle of
  incidence
• ?1 ?1
• The incident ray, the reflected ray and the
  normal are all in the same plane

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Index of Refraction, n

• Property of medium

V and wavelength change Frequency ( f )
does NOT change
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Refraction
Bending of light
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Reflected and Refracted Rays

• Ray ? is the incident ray
• Ray ? is the reflected ray
• Ray ? is refracted into the lucite
• Ray ? is internally reflected in the lucite
• Ray ? is refracted as it enters the air from the
  lucite

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Law of Refraction

• The incident ray, the reflected ray, the
  refracted ray, and the normal all lie on the same
  plane

• n1 sin ?1 n2 sin ?2

( Snells Law )
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Snells Law Example

• Light is refracted into a crown glass slab
• ?1 30.0o
• Question ?2 ?
• n1 1.00 and n2 1.52
• From Table 35.1
• ?2 sin-1(n1 / n2 ) sin ?1
• 19.2o

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Law of Refraction -- diagram for proof