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Coherence (physics), the quality of a wave to display a well defined phase relationship in different regions of its domain of definition; Hilbert transform, a method of changing phase by 90° Reflection phase shift, a phase change that happens when a wave is reflected off of a boundary from fast medium to slow medium
All those waves have the same frequency. In parametric pumping, the parameters of the medium are modulated by the pump wave at double frequency. The interaction of this perturbation with the incident wave will produce the conjugate wave. Both techniques allow an amplification of the conjugate wave compared to the incident wave. [1]
Phase velocity is the rate at which the phase of the wave propagates in space: any given phase of the wave (for example, the crest) will appear to travel at the phase velocity. The phase velocity is given in terms of the wavelength λ (lambda) and period T as v p = λ T . {\displaystyle v_{\mathrm {p} }={\frac {\lambda }{T}}.}
The coherence of two waves expresses how well correlated the waves are as quantified by the cross-correlation function. [7] [1] [8] [9] [10] Cross-correlation quantifies the ability to predict the phase of the second wave by knowing the phase of the first. As an example, consider two waves perfectly correlated for all times (by using a ...
Light waves change phase by 180° when they reflect from the surface of a medium with higher refractive index than that of the medium in which they are travelling. [1] A light wave travelling in air that is reflected by a glass barrier will undergo a 180° phase change, while light travelling in glass will not undergo a phase change if it is reflected by a boundary with air.
For example, phase–amplitude coupling is where the phase of a slow wave is coupled with the amplitude of a fast wave. [70] The theta-gamma code is a coupling between theta wave and gamma wave in the hippocampal network. During a theta wave, 4 to 8 non-overlapping neuron ensembles are activated in sequence.
Phase shifts themselves are invisible, but become visible when shown as brightness variations. When light waves travel through a medium other than a vacuum, interaction with the medium causes the wave amplitude and phase to change in a manner dependent on properties of the medium. Changes in amplitude (brightness) arise from the scattering and ...
The previous definition of phase velocity has been demonstrated for an isolated wave. However, such a definition can be extended to a beat of waves, or to a signal composed of multiple waves. For this it is necessary to mathematically write the beat or signal as a low frequency envelope multiplying a carrier. Thus the phase velocity of the ...