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What are Stationary Waves?
In physics, stationary waves are also called standing waves. It is a wave that spins in time but whose peak magnitude does not move in space. A stationary wave is formed by combining two waves that move in opposite directions with the same amplitude and frequency.
This phenomenon happens due to the interference of two overlapping waves, and their energies are added or cancelled. Faraday first noticed standing waves in 1831. The phenomenon of resonance is the most common cause of standing waves in which the interference of waves reflected back and forth at the resonance frequency of the resonator causes standing waves to form inside the resonator.
Using resonance, standing waves can be produced or induced mechanically in a solid medium. A simple example to understand standing waves is the shaking of rope from either end of a jumping rope. If the rope is shaken in synchronization, then the rope will form a regular pattern of nodes and antinodes that appears to be stationary hence named standing or stationary waves.
A progressive wave generally travels continuously without changing its direction in a medium with the same amplitude. It is also known as a traveling wave or progressive wave. The continuous movement of particles in a medium generates a progressive wave.
The velocity of this wave is measurable or has a velocity with which it travels. In progressive waves, energy flow and waves are unidirectional, and energy flows in wave direction. All particles are motile, and no particle is in resting condition. The amplitude of particle travels is the same in all particles.
The energy transfer is from one particle to another, propelling it forward in a progressive wave. There are two kinds of progressive waves longitudinal waves and transverse waves. The progressive traits are amplitude, wavelength, velocity, frequency, and periodicity.
In the natural world, progressive waves are created when an object undulates and sends waves to travel over space. Common examples of progressive waves are ocean waves generated by wind. The movement of sound from the air is also an example of a progressive wave.
Difference Between Stationary and Progressive Waves
A type of wave that appears stationary with specific points on the wave remaining static while others move back and forth in a regular rhythm is called a stationary wave. There are various examples of stationary waves, e.g., a vibrating string, a resonant cavity, and an oscillating system such as an electronic circuit.
At the same time, A progressive wave generally travels continuously without changing its direction in a medium with the same amplitude. The typical examples of traveling waves are sound waves traveling through the air and water waves on oceans due to air. The particle of the medium moves back and forth in a fixed position as the wave pass through, but the direction of the wave remains in a specific direction.
Another critical difference between stationary and progressive waves is that the stationary wave does not travel through the medium, while the traveling wave moves through the medium.
The reflection of waves by a boundary and interference with each other creates stationary waves. In contrast, the traveling wave is by motion created by the vibration of particles or sources.
Comparison Between Stationary and Progressive Waves
|Parameter||Stationary Wave||Travelling Wave|
|Energy transfer||No energy transfer occur.||Energy transfers from one particle to other.|
|Amplitude||Amplitude varies at nodes and antinodes.||All particles are with the same amplitude.|
|Nodes and antinodes||Stationary waves have nodes and anti-nodes.||There are no nodes and Antinodes in a traveling wave.|
|Wavelength||Same as the component wave.||The distance between adjacent particles is in phase.|
|Wave shape||Static wave||Propagate in the direction of the wave with speed.|
- Beni, G. and Hackwood, S., 1992, August. Stationary waves in cyclic swarms. In Proceedings of the 1992 IEEE International Symposium on Intelligent Control (pp. 234-242). IEEE.
- Cornish, V., 1907. Progressive waves in rivers. The Geographical Journal, 29(1), pp.23-31.