
Near and Far Field - peter_d_sherman
https://en.wikipedia.org/wiki/Near_and_far_field
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peter_d_sherman
>"The near field and far field are regions of the electromagnetic field (EM)
around an object, such as a transmitting antenna, or the result of radiation
scattering off an object. Non-radiative 'near-field' behaviors dominate close
to the antenna or scattering object, while electromagnetic radiation 'far-
field' behaviors dominate at greater distances.

Far-field E (electric) and B (magnetic) field strength decreases as the
distance from the source increases, resulting in an

 _inverse-square law_

for the radiated power intensity of electromagnetic radiation. By contrast,
near-field E and B strength decrease more rapidly with distance: the radiative
field decreases by the

 _inverse-distance squared_

, the reactive field by an

 _inverse cubed law_

, resulting in a diminished power in the parts of the electric field by an

 _inverse fourth-power and sixth-power_

, respectively. The rapid drop in power contained in the near-field ensures
that effects due to the near-field essentially vanish a few wavelengths away
from the radiating part of the antenna."

PDS: Boy, it sure seems that antennas and EM fields have all sorts of

 _inverse N power_

laws governing various properties/attributes/aspects of them.

I think that it would be an interesting future project to first enumerate all
of the N power properties/attributes, and then see if there are any gaps in
that table, for example, what field or fields are produced which decline
relative to distance and the inverse fifth power?

Or, if there turns out to be none... then how would such a field or fields be
created? And how would they be measured?

Oh, it might not have any applications!

But it would be tremendous for _understanding_...

Anyway, I think there might be a lot of room for research in this area...

Not all antennas, fields, power sources, frequency generators, mixers, and
field calculaton math, are created equal, let's remember...

