Stationary waves are formed by two identical waves travelling in opposite directions

Wave Types, Polarisation & Stationary Waves — AQA A-Level Physics

Key Definition

Stationary wave — A wave pattern produced by the superposition of two waves of the same frequency and amplitude travelling in opposite directions. Usually formed by a wave and its reflection.

Stationary waves store energyThe capacity to do work. Measured in joules (J).. Progressive waves transfer energyThe capacity to do work. Measured in joules (J)..
The peaks and troughs of a stationary waveA wave pattern formed by the superposition of two progressive waves of the same frequencyThe number of complete oscillations passing a point per unit time. Measured in hertz (Hz). and amplitudeThe maximum displacement of a point on a wave from its equilibrium (rest) position. Measured in metres (m). travelling in opposite directions. EnergyThe capacity to do work. Measured in joules (J). is not transferred along a stationary wave. do not move along the medium.
Each point on the stationary waveA wave pattern formed by the superposition of two progressive waves of the same frequencyThe number of complete oscillations passing a point per unit time. Measured in hertz (Hz). and amplitudeThe maximum displacement of a point on a wave from its equilibrium (rest) position. Measured in metres (m). travelling in opposite directions. Energy is not transferred along a stationary wave. has a different amplitudeThe maximum displacement of a point on a wave from its equilibrium (rest) position. Measured in metres (m). (unlike a progressive waveA wave that transfers energy from one place to another without transferring matter. where every point has the same amplitude).

Progressive vs stationary waves

Progressive: all points have the same amplitude. Stationary: each point has a different amplitude.
Progressive: energy is transferred along the wave. Stationary: energy is stored, not transferred.
Progressive: does not have nodes or antinodes. Stationary: has nodes and antinodes.
Progressive: points exactly one wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m). apart are in phase. Stationary: points between adjacent nodes are in phase; points on opposite sides of a nodeA point on a stationary wave where the displacement is always zero. Located at half-wavelength intervals. are in antiphase.