14. Waves, Sound, & Physical Optics

Slideshows: Unit 14 Waves, Sound, & Physical Optics Slides (under construction);
Previous notes from AP1's unit 9 prior to 2020 Waves and Sound Notes

Textbook: Chapters 20 in Mastering Physics (get online code for registration on about page of google classroom)

Objectives (out of date - update soon):

•  Classifying/defining/describing waves

  • Waves are traveling disturbances that transfer energy and momentum without transferring mass.

  • differentiate between longitudinal and transverse waves. 

  • mechanical waves require a medium. electromagnetic waves do not.

  • Explain waves (like sound) in terms of a transfer of energy and momentum.

  • The energy of waves (like sound) depends on and increases with amplitude. 

• Wave properties

  • Understand how to measure and explain the following:

    • amplitude

    • frequency (cycles per second)

    • period (repeat time)

    • wavelength (repeat distance or ration of v/ƒ)

    • wave speed

    • energy

  • wave speed is dependent on the medium, not ƒ or λ

  • observed wave frequency can be altered by relative motion between the source and the observer

• 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.

  • colliding waves 

    • pass through each other, rather than bounce back

    • add their displacements (superposition)

    • can produce amplitude variations if not the same frequency

  • standing waves

    • explain using reflection principles for confined waves

    • identify nodes and anti-nodes

    • explain examples of stringed and tubed instruments

    • possible wavelengths depend on the size of the region the waves are confined to

  • Explain beats based on frequency difference

  • 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.

Equations: 

There is only 1 primary equation: 

In addition, you should know these variations/derivations: 

Common Misconceptions: (these statements all have errors)

• • Waves transport matter.

  • Waves do not have energy.

  • All waves travel the same way.

  • Frequency is connected to loudness for all amplitudes.

  • Big waves travel faster than small waves in the same medium.

  • Different colors of light are different types of waves.

  • Pitch is related to intensity.

  • There must be a medium for a wave to travel through.

External Resources

• Waves on a string simulator: https://phet.colorado.edu