OCR AS Physics

Revision Notes

4.9.9 Nodes & Antinodes

Nodes & Antinodes

  • A stationary wave is made up nodes and antinodes
    • Nodes are regions where there is no vibration
    • Antinodes are regions where the vibrations are at their maximum amplitude
  • The nodes and antinodes do not move along the string
    • Nodes are fixed and antinodes only move in the vertical direction
  • The phase difference between two points on a stationary wave are either in phase or out of phase
    • Points between nodes are in phase with each other
    • Points that have an odd number of nodes between them are out of phase
    • Points that have an even number of nodes between them are in phase
  • The image below shows the nodes and antinodes on a snapshot of a stationary wave at a point in time

Nodes and antinodes, downloadable AS & A Level Physics revision notes

  • Where:
    • L is the length of the string
    • One wavelength λ is only a portion of the length of the string

Worked Example

A stretched string is used to demonstrate a stationary wave, as shown in the diagram.

WE - Nodes and Antinodes question image(1), downloadable AS & A Level Physics revision notes

Which row in the table correctly describes the length of L and the name of X and Y?

WE - Nodes and Antinodes question image(2), downloadable AS & A Level Physics revision notes

ANSWER: C
Worked example - nodes and antinodes (2), downloadable AS & A Level Physics revision notes

Exam Tip

Make sure you learn the definitions of node and antinode:

  • Node = A point of minimum or no disturbance
  • Antinode = A point of maximum amplitude

In exam questions, the lengths of the strings will only be in whole or half wavelengths. For example, a wavelength could be made up of 3 nodes and 2 antinodes or 2 nodes and 3 antinodes.

Calculating Wavelength from Nodes & Antinodes

  • The wavelength λ of a stationary wave can be determined by the separation between adjacent nodes (or antinodes)

The separation between adjacent nodes or antinodes is equal to λ / 2

  • Adjacent means two nodes or antinodes that are next to each other

Worked Example

The stationary wave below has a length L of 15 cm.

 

Calculate the wavelength λ of the wave.

Step 1: Calculate the distance between two nodes

Distance between two nodes = 15 cm ÷ 3 = 5 cm

Step 2: Calculate λ

Distance between two nodes = λ / 2 = 5 cm

λ = 2 × 5cm = 10 cm

Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top