See also: Phase

The phase indicates the instantaneous situation in the cycle, of a size which varies recurringly.

Mathematical representation

In the case of a sinusoidal wave, if $A\_0$ is the amplitude, $\backslash \; omega$ the pulsation (in rad. S ^-1), $k$ the Number of wave (in m^-1), $t$ time (in seconds) and $x$ the position, we can write:

$A\; (X,\; \backslash ,\; T)\; =\; A\_0\; \backslash ,\; sin\; (\backslash \; Omega\; \backslash ,\; T\; -\; K\; \backslash ,\; X\; +\; \backslash \; alpha)$

The phase totale corresponds to: $(\backslash \; Omega\; \backslash ,\; T\; -\; K\; \backslash ,\; X\; +\; \backslash \; alpha)$

The phase initiale (when $x$ and $t$ are null) is: $\backslash \; alpha$.

The phase is a size without unit.

One cannot know the total phase of a wave, at one moment and a given place, by a simple measurement if his equation in advance is not known. It is initially necessary to do a sampling with several steps of time to obtain the total cycle of the wave. In reality, the value of the total phase of a wave is thus not very useful. The size which is really useful is the difference in phase or Déphasage between two places, two moments or two waves.

See too

Related articles

• Wave
• Dephasing
• Interference

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