32
NormalNormalLineLine
More Dense
Less Dense
WATERWATER
AIRAIR
Normal Normal Line #1Line #1
SlowSlow
FastFast
Light BeamLight Beam
AIRAIR
NormalNormalLineLine
More Dense
Less Dense
WATERWATER
AIRAIR
Normal Normal Line #1Line #1
SlowSlow
FastFast
Light BeamLight Beam
FastFastAIRAIR
Normal Normal Line #2Line #2
Refraction ExamplesRefraction Examples
• Light slows down when it goes from air into water and bends toward the normal.
• An Analogy: A car slows down when it goes from pavement onto gravel and turns toward the normal.
• An Illusion : Fish in the water appear closer and nearer the surface. (See Figure 28.27)
http://cougar.slvhs.slv.k12.ca.us/~pboomer/physicslectures/secondsemester/light/refraction/refraction.html
RefractionRefraction
WATER
AIR
Observer
True Fish
False Fish
LensesLenses• Diverging Lens
• A lens that is thinner in the middle than at the edges, causing parallel light rays to diverge.
• Converging Lens• A lens that is thicker in the middle and
refracts parallel light rays passing through to a focus.
C F CF
Diverging or Diverging or Concave LensConcave Lens
C F CF
Converging or Converging or Convex LensConvex Lens
C F CF
Converging Converging or Convex or Convex
LensLens
C F CF
Converging Converging or Convex or Convex
LensLens
C F CF
Converging Converging or Convex or Convex
LensLens
C F CF
Converging Converging or Convex or Convex
LensLens
C F CF
Converging Converging or Convex or Convex
LensLens
Myopia (Near-Sightedness)
People with near-sightedness cannot see clearly at distance.
Hyperopia (Farsightedness)
People with far-sightedness cannot see clearly up close
Total Internal Reflection...Total Internal Reflection...
…is the total reflection of light traveling in a medium when it strikes
a surface of a less dense medium
WATER
AIR
Light Light SourceSource
Critical AngleCritical Angle
Total Total Internal Internal
ReflectionReflection
RefractionRefraction
http://cougar.slvhs.slv.k12.ca.us/~pboomer/physicslectures/secondsemester/light/refraction/refraction.html
• Total Internal Reflection occurs when the angle of incidence is greater than the critical angle.
• The critical angle for an air-water interface is 48°.
• Fish can see everything above the water’s surface in a 96° cone of vision.
• Demo - Laser and light pipe
http://cougar.slvhs.slv.k12.ca.us/~pboomer/physicslectures/secondsemester/light/refraction/refraction.html
Dispersion...Dispersion...• …is the separation of white light into pure colors (ROY G. BIV).
• Dispersion Examples: • Prisms• Diffraction Gratings• CD’s• Raindrops
RainbowsRainbows• Raindrops refract, reflect and disperse sunlight.
• Rainbows will always appear opposite of the Sun in the sky.
• You cannot run from or run to a rainbow!
