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The sign convention is chosen for consistency with propagation in lossy media. If the attenuation constant is positive, then the wave amplitude decreases as the wave propagates in the x-direction. Wavelength, phase velocity, and skin depth have simple relationships to the components of the wavenumber:
The phase velocity is the rate at which the phase of the wave propagates in space. The group velocity is the rate at which the wave envelope, i.e. the changes in amplitude, propagates. The wave envelope is the profile of the wave amplitudes; all transverse displacements are bound by the envelope profile.
Wave speed is a wave property, which may refer to absolute value of: . phase velocity, the velocity at which a wave phase propagates at a certain frequency; group velocity, the propagation velocity for the envelope of wave groups and often of wave energy, different from the phase velocity for dispersive waves
Dispersion occurs when sinusoidal waves of different wavelengths have different propagation velocities, so that a wave packet of mixed wavelengths tends to spread out in space. The speed of a plane wave, , is a function of the wave's wavelength : = ().
For an incident wave traveling from one medium (where the wave speed is c 1) to another medium (where the wave speed is c 2), one part of the wave will transmit into the second medium, while another part reflects back into the other direction and stays in the first medium. The amplitude of the transmitted wave and the reflected wave can be ...
The speed of propagation of a wave is equal to the wavelength divided by the period, or multiplied by the frequency: v = λ τ = λ f . {\displaystyle v={\frac {\lambda }{\tau }}=\lambda f.} If the length of the string is L {\displaystyle L} , the fundamental harmonic is the one produced by the vibration whose nodes are the two ends of the ...
From the basic one-dimensional plane-wave solutions, a general form of a wave packet can be expressed as (,) = (()). where the amplitude A(k), containing the coefficients of the wave superposition, follows from taking the inverse Fourier transform of a "sufficiently nice" initial wave u(x, t) evaluated at t = 0: = (,) . and / comes from Fourier ...
A wave packet has an envelope that describes the overall amplitude of the wave; within the envelope, the distance between adjacent peaks or troughs is sometimes called a local wavelength. [21] [22] An example is shown in the figure. In general, the envelope of the wave packet moves at a speed different from the constituent waves. [23]