Standing wave facts for kids

Standing wave in stationary medium. The red dots represent the wave nodes. A standing wave (black) depicted as the sum of two propagating waves traveling in opposite directions (red and blue).

Electric force vector (E) and magnetic force vector (H) of a standing wave. Standing waves in a string — the fundamental mode and the first 6 overtones.

A two-dimensional standing wave on a disk; this is the fundamental mode A higher harmonic standing wave on a disk with two nodal lines crossing at the center.

In physics, a standing wave – also called a stationary wave – is a wave that oscillates in one constant position.

The word oscillate simply describes the vibrating movement of particles in a medium when acted upon by a wave, or the regular up and down motion shown in the animation. Oppositely to a progressive (moving) wave, stationary waves do not transfer energy in a given direction when they oscillate.

When a guitar string is plucked, for example, a stationary wave is formed. This happens because on releasing the string, two progressive waves move down the string in opposite directions. When they reach the point where the string is tied down, they cannot move beyond this boundary. At the boundary, the wave is reflected and travels back in the opposite direction. The two reflected waves meet and interfere with one another. Superposition occurs, the opposing directions of the reflected waves cancel out resulting in one stationary wave.

Images for kids

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  Animation of a standing wave (red) created by the superposition of a left traveling (blue) and right traveling (green) wave

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  Longitudinal standing wave

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  Standing waves in a string – the fundamental mode and the first 5 harmonics.

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  Molecular representation of a standing wave with n = 2 for a pipe that is closed at both ends. Considering longitudinal displacement, note that the molecules at the ends and the molecules in the middle are not displaced by the wave, representing nodes of longitudinal displacement. Halfway between the nodes there are longitudinal displacement anti-nodes where molecules are maximally displaced. Considering pressure, note that the molecules are maximally compressed and expanded at the ends and in the middle, representing pressure anti-nodes. Halfway between the anti-nodes are pressure nodes where the molecules are neither compressed nor expanded as they move.

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  Standing waves in a string – the fundamental mode and the first 5 harmonics.

See also

In Spanish: Onda estacionaria para niños