Antinode
An antinode is a point in a standing wave where the displacement of the medium reaches its maximum amplitude, caused by constructive interference between the two superposed waves. Antinodes oscillate with the greatest energy in the standing wave pattern and are located exactly halfway between consecutive nodes, at intervals of half a wavelength. They are the positions of maximum vibration in musical instrument strings and air columns.
Comparison of Nodes and Antinodes
| Feature | Node | Antinode |
|---|---|---|
| Displacement | Zero (always) | Maximum (oscillates) |
| Interference type | Destructive | Constructive |
| Position | Every λ/2 from last node | Midway between nodes |
| Energy | Potential energy maximum | Kinetic energy maximum |
| Motion | Stationary | Oscillates with full amplitude |
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Related Terms
Node (wave)
A node is a point in a standing wave where the displacement of the medium is permanently zero due to destructive interference between the two superposed waves. Nodes remain stationary regardless of time, and they occur at intervals of half a wavelength (λ/2) along the medium. In a vibrating string fixed at both ends, the fixed endpoints are always nodes, and the number of nodes determines the harmonic mode of vibration.
Standing Wave
A standing wave is a wave pattern formed by the superposition of two identical waves travelling in opposite directions, resulting in a stationary pattern of nodes (zero displacement) and antinodes (maximum displacement). Standing waves do not transport energy along the medium; instead, energy oscillates between kinetic and potential forms at fixed positions. They are fundamental to the physics of musical instruments, laser cavities, and microwave resonators.
Amplitude
Amplitude is the maximum displacement of a wave from its equilibrium (rest) position, representing the "height" of a wave. It is denoted by A and measured in metres for mechanical waves, or in volts, pascals, or other units depending on context. Amplitude is directly related to the energy carried by the wave: the greater the amplitude, the greater the energy, which is why louder sounds and brighter lights have larger amplitudes.
From Greek/Latin "anti" (against, opposite) + "nodus" (knot). An antinode is the opposite of a node — the point of maximum movement rather than zero movement.