## inverse square vs cube = ???

If the electric field falls off at the inverse square ratio, and magnetic at inverse cube, does EM radiation dissipate at 1/r^5 ratio for circularly polarized waves?
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 Recognitions: Gold Member No, the inverse cube applies to the magnetic strength of a magnet, not the magnetic field of an EM wave. Remember that an EM wave is a disturbance in the EM field that carries energy, it is not the force from a magnet. The magnetic field of the EM wave really isn't a "field" like you would describe around a magnet, but an oscillating field vector. What I'm getting at is that if you let out a quick "pulse" of light and followed right behind the wavefront you will not feel a force from either the electric or magnetic fields of the EM wave because they are not sources of charge like a particle or magnet is, but a change in the EM field. I hope that makes sense.
 Thanks so much for the reply! Let me be more specific. Say I have a sphere, free space capacitance. Radius is .75. Around the equator you have an inductance (disk, close approximation for modeling cube ratio at close distance) periphery 1.5.

## inverse square vs cube = ???

Got cut off... Radius 1.5, say the say the wave length is such that the quarter (90 degrees) periphery falls at radius 6. At r=3 both electric at in inverse sqare and magnetic at inverse cube, are equal both in terms of intensity (0.707) in terms of phase relation and square vs cube relationship. I why is it not a 1/r^5 at this point. Near field.

 Quote by Drakkith but a change in the EM field.
What EM field? The EM field emitted by the antenna?

Oh, and light does induce some sort of pressure when it hits objects.

 Recognitions: Gold Member Science Advisor @counterphit The inverse square law doesn't apply in the near field of a radiating dipole (so what you say is reasonable). In the near field, the magnetic and electric fields have different ratios but settle down to a constant ratio at a distance. Not only do the amplitudes change but also the phases. They are more or less in quadrature right next to the radiator but, once the fields are purely radiative, they are in phase and the ISL kicks in (for the Power flux density).

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 Quote by Menaus What EM field? The EM field emitted by the antenna?
The EM field in space. The change is caused by accelerating charges in an antenna. (Among other ways)

 Oh, and light does induce some sort of pressure when it hits objects. http://en.wikipedia.org/wiki/Radiation_pressure
Of course it does, it carries energy and momentum with it.

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