Stationary Waves:

When an advancing wave is reflected from an obstacle, into the same medium, we have two equal waves (same frequency and wave length) travelling in opposite directions superimposed on each other.



The interference of the two waves produces a stationary wave in the medium so that in some regions the particles of the medium are permanently at rest, and at certain other regions the particles undergo maximum and minimum displacements alternatively. The regions where the particles are permanently at rest are called nodes and the antinodes. The wavelength of a stationary wave is the distance between two alternate antinodes or two alternate nodes

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