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Nodes and antinodes
Intermediate
Points of no motion and maximum motion.
Nodes are points that never move; antinodes oscillate with the maximum amplitude. Adjacent nodes are λ/2 apart.
A string of 1 m vibrating in the third harmonic has 4 nodes.
A closed end is a displacement node, an open end an antinode (for air).
In more detail
Nodes are points where the displacement is always zero, and antinodes are points where it is at its maximum. They alternate along a standing wave, spaced by half a wavelength.
Real-world uses
- Tuning forks produce standing waves with nodes at their stems.
- Engineers avoid placing sensitive equipment at antinodes of vibration.
- A jump rope held at its ends shows nodes at the ends and antinodes in the middle when it vibrates.
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Frequently asked questions
Where are nodes on a string fixed at both ends?
At both ends and at regular intervals of half a wavelength between them.
Why do antinodes oscillate most?
Because the two waves reinforce there, giving the largest amplitude.
Is a node the same as a point of no energy?
No. A node has no displacement, but the energy is still stored in the oscillating region around it.
Related topics in Waves & Sound
Path difference and phase · Beats · Standing waves · Modes of a stretched string · Harmonics and overtones · Open organ pipe