group velocity


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Group velocity

The velocity of propagation of a group of waves forming a wave packet; also, the velocity of energy flow in a traveling wave or wave packet. The pure sine waves used to define phase velocity vp do not ever really exist, for they would require infinite extent. What do exist are groups of waves, wave packets, which are combined disturbances of a group of sine waves having a range of frequencies and wavelengths. Good approximations to pure sine waves exist, provided the extent of the media is very large in comparison with the wavelength of the sine wave. In nondispersive media, pure sine waves of different frequencies all travel at the same speed vp, and any wave packet retains its shape as it propagates. In this case, the group velocity vg is the same as vp. But if there is dispersion, the wave packet changes shape as it moves, because each different frequency which makes up the packet moves with a different phase velocity. If vp is frequency-dependent, then vg is not equal to vp. See Phase velocity, Sine wave, Wave motion

group velocity

[¦grüp və′läs·əd·ē]
(physics)
The velocity of the envelope of a group of interfering waves having slightly different frequencies and phase velocities.
References in periodicals archive ?
Moreover, the velocity of propagation of the envelope in measurements and in computations based on the Dysthe equation is markedly higher than the linear group velocity as assumed in the NLS equation.
In fact, if inserting Equation (15) into Equation (53) we can obtain the group velocity of the particle [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] constant.
Thus, the group velocity of the microscopic particle is found out from
Periods of G waves lie in the range from about 50 to 350s, corresponding to a flat portion of the group velocity curve for Love waves, which has been extended up to periods of around 700s (Burne, Benioff and Ewing 1961).
the group velocity is less than the shear wave velocity in the upper mantle.
3 we have plotted the variation in dimensionless group velocity U/[[beta].
We present a self-consistent approach based on group velocity formalism for analyzing time-of-flight data.
as already discussed and the energy flux propagates with the so-called group velocity [v.
4, which shows the polar plot representation for group velocity [v.
Therefore, a convenient way of representing the group velocity is shown in Fig.
The publisher supplies a web site with notes and other information, and Parker offers appendices on probability theory and statistics and group velocity.
Each of these travels at a slightly different group velocity through the fiber, and causes a group delay and consequently dispersion.