Long wavelength limit - Alchetron, The Free Social Encyclopedia

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 λ >> a , where a is the size of the system. The following statements are all equivalent:

λ >> a

k a << 1 , where k is the wave vector

ω c a << 1 , where ω is the angular frequency, c is the propagation speed of waves.

References

Long wavelength limit Wikipedia

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