Standing Waves

A standing waveor a stationary wave, is a wave that has parts that remain in a constant position. This can occur when the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves travelling in opposite directions. In the second case, for waves of equal amplitude travelling in opposing directions, there is on average no net propagation of energy.

Nodes (red dots) are points of no vibration and antinodes are points of maximum vibration. Look at the following animation to see how the standing wave envelope is formed...

Faraday waves, also known as Faraday ripples, are nonlinear standing waves that appear on liquids enclosed by a vibrating receptacle. They are named after Michael Faraday, who first described them in an appendix to an article in the Philosophical Transactions of the Royal Society of London in 1831.

If a layer of liquid is placed on top of a vertically oscillating platform, a pattern of standing waves appears which oscillates at half the driving frequency. These waves can take the form of stripes, close-packed hexagons, or even squares or quasiperiodic patterns. Faraday waves are commonly observed as fine stripes on the surface of wine in a wineglass that is ringing like a bell.

This vidclip is really cool - the physics of these waves is outside the scope of this site but wow!