IB DP Physics: SL复习笔记4.5.2 Nodes & Antinodes

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

Worked Example

Which row in the table correctly describes the length of L and the name of X and Y?WE-Nodes-and-Antinodes-question-image2