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Re: Inverse Square 'law' Re: About wireless energy transfer



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 09:43 PM 2/14/2007, Tesla list wrote:
Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Phil,

I believe that the energy density (if I may) is inversely proportional to the cross sectional area. Assuming no absorption, the total energy flowing thru any cross sectional area will be the same as any other area (area being what is occuppied by the beam at any point). So, if a non diverging beam passes thru a focusing lens, the energy density will increase as the area of the beam is decreased. If one measures distance from the focal point and compares two cross sectional areas within the converging beam, the energy density would follow an inverse square law.



Indeed it would..


Also, keep in mind "converging beam" implies a means of making that beam which is large compared to a wavelength. And, that the converging eventually comes to a limit, and then starts expanding. All the classic "inverse square law" really only applies in the far field, where the source can be treated as a point.

Such things (e.g. geometric optics) are used in reflector antenna designs all the time.



Gerry R.


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, February 10, 2007 9:28 PM
Subject: Re: Inverse Square 'law' Re: About wireless energy transfer


Original poster: FIFTYGUY@xxxxxxx
In a message dated 2/10/07 6:58:19 P.M. Eastern Standard Time, tesla@xxxxxxxxxx writes:

>It sounds like the only way to "not have an inverse square
>relationship" is to have a beam that has absolutely NO DIVERGENCE and
>physics would preclude this.

    Wouldn't a *converging* beam have an "inverse inverse square law"?

-Phil LaBudde