منابع مشابه
Group velocity
A short and largely traditional review of the concept of group velocity, prepared for the forthcoming Encyclopedia of Nonlinear Science Waves often propagate as a packet, or group, within which there are several wave crests. A common illustration is given by the wave pattern formed when a stone is thrown into a pond. An axially symmetric ring of waves on the water surface propagates outwards as...
متن کاملNote on Group Velocity and Energy Propagation
A general proof is given for the equality between group velocity and energy velocity for linear wave propagation in a homogeneous medium with arbitrary spatial and temporal dispersion. In the series of physics “Questions” in the American Journal of Physics, K. M. Awati and T. Howes ask for a general proof of the fact that in linear dispersive wave propagation, energy propagates at the group vel...
متن کاملNegative Group Velocity
In more detail, consider a classical model of matter in which spectral lines are associated with oscillators. In particular, consider a gas of atoms with two closely spaced spectral lines of angular frequencies ω1,2 = ω0 ± Δ/2, where Δ ω0. Each line has the same damping constant (and spectral width) γ. Ordinarily, the gas would exhibit strong absorption of light in the vicinity of the spectral ...
متن کاملEnhanced group velocity in metamaterials
The Bruggeman formalism is implemented to estimate the refractive index of an isotropic, dielectric, homogenized composite medium (HCM). Invoking the well–known Hashin– Shtrikman bounds, we demonstrate that the group velocity in certain HCMs can exceed the group velocities in their component materials. Such HCMs should therefore be considered as metamaterials. PACS numbers: 41.20.Jb, 42.25.Dd, ...
متن کاملOn the group velocity of guided waves in drill strings.
A key element to verify the drill-bit signal processing is the estimation of the time delay of the guided waves transmitted through the drill string from the bit to the surface. This delay can be measured from drill-bit vibrations or calculated using the mechanical properties of the drill string. The calculation of the complete solution and the exact dispersion relations requires expensive nume...
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ژورنال
عنوان ژورنال: Proceedings of the London Mathematical Society
سال: 1904
ISSN: 0024-6115
DOI: 10.1112/plms/s2-1.1.473