- 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
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?
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.
- 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
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