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

[Shachar Shemesh]

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?

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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