8-Mechanical Waves

Slideshows:Waves and Sound Notes

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

Objectives:

  • 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
  • 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

Equations:

There is only 1 primary equation:

In addition, you should know these variations/derivations:

Terms to know:

Make your own flash cards or use the electronic ones I made at quizlet.com (or in the Quizlet app on your phone) and here is the link for them: https://quizlet.com/_25opqj.

Additional help:

Here is a graphic to help keep straight which harmonics are which for the 3 classes of instruments:

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