Stationary Waves

Question 1

How are stationary waves produced?

Answer 1

• Stationary waves are produced by the superposition of two progressive waves of the same frequency (and wavelength) and similar amplitude traveling in opposite directions
• This is usually achieved by a traveling progressive wave and its reflection (guitar string)
• The superposition produces a wave pattern where the peaks and troughs do not move
• Stationary waves store energy, unlike progressive waves which transfer energy

Question 2

What are the differences between a progressive wave and stationary wave?

Answer 2

• In progressive waves:
  
  • All points have same amplitude
  • Points exactly one wavelength apart
    are in phase (phase of points
  • Energy is transferred
  • Has no nodes and antinodes
  • Wave speed is speed at which wave
    moves through medium
• In stationary waves:
  
  • Each point has different amplitude
    depending on superposition
  • Has nodes (points of destructive
    interference) and antinodes (points of
    constructive interference)
  • Points between nodes are in phase,
    points that have an odd number of
    nodes between them are out of
    phase (if even number they are in
    phase)
  • Each point on wave oscillates at
    different speeds (wave doesn’t move)

Question 3

What are nodes and antinodes?

Answer 3

• Nodes are regions where there is no vibration in a stationary wave
• Antinodes are regions where the vibrations are at their maximum amplitude in a stationary wave