Stationary and Progressive waves

By definition, a stationary or standing wave is formed when two progressive waves of equal amplitude and frequency are travelling in opposite direction and combined together.

Stationary waves are obtained as a result of reflection of the incident wave. When a wave travels along a given path and it is reflected perpendicularly on striking an obstacle, the wave returns along the same path. The resultant wave from the two waves is a stationary wave.

All other waves, which spread out continuously, either transverse or longitudinal are called progressive or travelling waves.

Nodes and Antinodes of stationary waves

Nodes

The node of a stationary wave is a point where there is no movement of the medium.

Antinodes

An antinode in a stationary wave is a point where there is maximum movement of the medium.

Examples of stationary waves

1. Standing waves in a string

2. Standing waves in a pipe.

A wave in an open or close pipe is a stationary wave

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