6-EM Waves & Optics

Notes: Optics Slideshow

Textbook: Chapter 21-24

Objectives & Essential Knowledge:

Wave properties

  • waves transfer momentum and energy, not matter
  • EM waves are transverse waves, but do not require a medium as they are oscillations of E and B fields.
  • transverse waves can be polarized (determine oscillation direction to pass through polarizers)
  • correlate amplitude (of either E or B field), wavelength and frequency between a graph and a sin or cosine function of the graph.

Wave Interactions

  • Apply superposition to predict or explain wave interference patterns (amplitudes are added)
  • Use huygen's principle to explain single slit and double slit interference - both the filling in of the shadow zone behind the barrier and the patterns on a far wall.

Geometric Optics

  • When light passes from one medium to another there will be some combination of
    • reflection: angle of incidence = angle of reflection for specular reflection
    • absorption:
    • refraction: speed change bends light according to snell's law
      • bends towards normal when going optically slower (more optically dense), away when higher
      • at a critical angle, the light is only refracted parallel to the surface
      • beyond the critical angle there is no refraction and only total internal reflection.
  • Image formation
    • reflection causes images to form with curved mirrors.
    • refraction causes images to form with curved lenses.
    • use ray diagrams to predict size, orientation and location of images formed.
    • use the thin lens equation to predict size, orientation and location of images formed.
    • Predict whether an image will be virtual or real.


Common Misconceptions:

  • Waves transport matter.
  • There must be a medium for a wave to travel through.
  • Waves do not have energy.
  • All waves travel the same way.
  • Different colors of light are different types of waves.
  • Light just is and has no origin.
  • Light is a particle.
  • Light is a mixture of particles and waves.
  • Light waves and radio waves are not the same thing.
  • In refraction, the characteristics of light change.
  • The speed of light never changes.
  • Rays and wave fronts are the same thing.
  • There is no interaction between light and matter.
  • The addition of all colors of light yields black.
  • Double slit interference shows light wave crest and troughs.
  • Light exits in the crest of a wave and dark in the trough.
  • In refraction, the frequency (color) of light changes.
  • Refraction is the bending of waves.