Refraction

• Light (electromagnetic radiation) travels at 3.0 x 10⁸ m/s in a vacuum. Light travels slower in other materials. It travels just slightly slower in air but with the number of significant digits we use, light travels at 3.0 x 10⁸ m/s in air as well. For other materials (glass, water etc.) light travels at a slower speed.
• Therefore light (electromagnetic radiation) refracts
  • graphic
  • car model to show direction
  • stress capitol R
• Relationship between <i and <R
  • not proportional
  • Snells Law
    • sin <i a sin <R
    • P336 Laws of Refraction
  • Example - If <i = 308, and <R=208,then
    • Is the ray going from faster to slower or visa versa
    • What is <R if <i changes to 408
      • (dealing with proportionalities and sin^-1 function)
• Index of Refraction
  • If one of the materials is a vacuum (or air) then the ratio sin<i / sin<R = n, the index of refraction for the material
  • example n_glass=1.52
  • Example p338 #2
  • Can n<1 ? Why?
• Generalized Snells Law
  • Graphic 2 materials
  • n₁=sin<i / sin<R₁
  • n₂=sin<i / sin<R₂
  • solve for sin<i and equate
  • n₁ sin<R₁ = n₂ sin<R₂
  • graphic and example
  • simplifies to index of refraction formula if one material is a vacuum or air (n=1)
• Applications
  • spear fishing
  • aquarium
  • scuba mask
  • lens
  • identification of materials