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
One wavelength on a stationary wave is only a proportion of its full length
- 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.
Which row in the table correctly describes the length of L and the name of X and Y?
ANSWER: C
Examiner 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.
Calculate the wavelength λ of the wave.