6130350856
Книга: Signal Velocity: Special Relativity, Wave, Group Velocity, Front Velocity, Dispersion (Optics), Phase Velocity, Velocity, Wavenumber, Dispersion Relation, Group Delay and phase Delay
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High Quality Content by WIKIPEDIA articles! The signal velocity is the speed at which a wave carries information. It describes how quickly a message can be communicated (using any particular method) between two separated parties. Every signal velocity is always slower than (or equal to) the speed of a light pulse in a vacuum (by Special Relativity). In the vast majority of cases, signal velocity is equal to group velocity (the speed of a short 'pulse' or of a wave-packet's middle or 'envelope'). However, in a few special cases (e.g., media designed to amplify the front-most parts of a pulse and then attenuate the back section of the pulse), group velocity can exceed even the vacuum speed of light. Signal velocity is always the same as front velocity.