4.5.2 Nodes & Antinodes

• A standing wave is made up nodes and antinodes
  • Nodes are locations of zero amplitude and they are separated by half a wavelength (λ/2)
  • Antinodes are locations of maximum amplitude

• The nodes and antinodes do not move along the wave
  • Nodes are fixed and antinodes only oscillate in the vertical direction

Nodes and antinodes of a stationary wave of wavelength λ on a string of length L at a point in time 

The Formation of Nodes and Antinodes

• Nodes are formed as a result of destructive interference
  • The amplitude of both waves cancel out
• Antinodes are formed as a result of constructive interference
  • The amplitude of both waves add together

Nodes and antinodes are a result of destructive and constructive interference respectively

• At the nodes:
  • The waves are in anti-phase meaning destructive interference occurs
  • This causes the two waves to cancel each other out

• At the antinodes:
  • The waves are in phase meaning constructive interference occurs
  • This causes the waves to add together

Phase on a Standing Wave

• Two points on a standing wave are either In Phase
  • Points that have an odd number of nodes between them are in anti-phase
  • Points that have an even number of nodes between them are in phase
  • All points within a "loop" are in phase

Points A, B and D are all in phase. While points A and D are in antiphase with point C

ANSWER: C