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What is the group velocity of evanescent waves?
https://arxiv.org/pdf/physics/9811001.pdfSTAR GIRL said:What is the group velocity of evanescent waves?
Thanksberkeman said:
The group velocity of evanescent waves refers to the speed at which the envelope or group of the wave propagates. It is different from the phase velocity, which is the speed at which the individual wave crests propagate.
The group velocity of evanescent waves is typically calculated using the complex wave number, which takes into account both the real and imaginary parts of the wave's propagation. It is also dependent on the refractive indices of the materials through which the wave is passing.
Understanding the group velocity of evanescent waves is important for various applications in optics and photonics, such as near-field microscopy, waveguides, and surface plasmon resonance. It also helps in the study of quantum mechanics and the behavior of particles at the nanoscale.
The group velocity of evanescent waves is affected by the angle of incidence, the refractive indices of the materials, and the frequency of the wave. It is also influenced by the thickness and composition of the materials through which the wave is propagating.
No, the group velocity of evanescent waves cannot be greater than the speed of light in a vacuum. This is because the wave itself does not actually travel faster than the speed of light, but rather the envelope of the wave appears to move faster due to the interference of the evanescent fields.