Long wavelength limit

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In electricity and magnetism, the long wavelength limit is the limiting case when the wavelength is much larger than the system size. This corresponds to the quasi-static case, and reduces to electrostatics and magnetostatics.

The physical criterion is that \lambda >> a, where a is the size of the system. The following statements are all equivalent:

  • \lambda >> a
  • ka << 1, where k is the wave vector
  • \frac{\omega}{c}a << 1, where \omega is the angular frequency, c is the propagation speed of waves.