Editing Standing wave (section)

== Standing wave ratio, phase, and energy transfer ==
{{Main|Standing wave ratio}}
If the two oppositely moving traveling waves are not of the same amplitude, they will not cancel completely at the nodes, the points where the waves are 180° out of phase, so the amplitude of the standing wave will not be zero at the nodes, but merely a minimum.  [[Standing wave ratio]] (SWR) is the ratio of the amplitude at the antinode (maximum) to the amplitude at the node (minimum).  A pure standing wave will have an infinite SWR.  It will also have a constant [[Phase (waves)|phase]] at any point in space (but it may undergo a 180° inversion every half cycle).  A finite, non-zero SWR indicates a wave that is partially stationary and partially travelling.  Such waves can be decomposed into a [[superposition principle|superposition]] of two waves: a travelling wave component and a stationary wave component.  An SWR of one indicates that the wave does not have a stationary component – it is purely a travelling wave, since the ratio of amplitudes is equal to 1.<ref>R S Rao, ''Microwave Engineering'', pp. 153–154, PHI Learning, 2015 {{ISBN|8120351592}}.</ref>

A pure standing wave does not transfer energy from the source to the destination.<ref>K A Tsokos, ''Physics for the IB Diploma'', p. 251, Cambridge University Press, 2010 {{ISBN|0521138213}}.</ref>  However, the wave is still subject to losses in the medium.  Such losses will manifest as a finite SWR, indicating a travelling wave component leaving the source to supply the losses.  Even though the SWR is now finite, it may still be the case that no energy reaches the destination because the travelling component is purely supplying the losses.  However, in a lossless medium, a finite SWR implies a definite transfer of energy to the destination.