[OT] Power over radio is it a true thing or just a myth ?

[Erez D]

2009/8/24 Shachar Shemesh <shachar at shemesh.biz>

>  Michael Vasiliev wrote:
>
> The power of the signal is inversely proportional to the square of
> distance.
>
>  That is not precisely accurate.
>
> An undirected point source of EM radiation (or any other type of energy)
> transmits energy that expands on a sphere from the point of transmittal. The
> surface area of the sphere expands proportionally to R^2. Therefor, the law
> of conservation of energy dictates that the energy received over a constant
> area receiver (say, a 1 cm^2 energy receiver) will decline proportionally to
> the square of the distance from the transmitter.
>
> As a side note - does that prove that our universe only has three
> dimensions?
>
it would if :
1. the origin of the signal is a point in all dimensions (which is usualy
not true as you transmit continusly in the time dimension(but may transmit a
pulse), dunno about other possible dimensions)
2. it is omnidirectional in all dimensions (which is not true either in the
time dimension, dunno about other dimensions as well)

AFAIK, according to general relativity, the world is 4D.
according to string theory, there are more dimensions ...

erez.


>
> However, if our transmitter is directional, and you keep the transmitter
> beam focused, so that it does not expand, there is no reason for the energy
> to almost not discard at all. Of course, the medium through which you
> transmit the energy may absorb some of it (assuming it is not a vacuum), and
> it may disperse some more of it, but there is no reason to get 1/R^2, or
> even 1/R.
>
> Shachar
>
> --
> Shachar Shemesh
> Lingnu Open Source Consulting Ltd.http://www.lingnu.com
>
>
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