Re: [Phys-l] spherical waves

[John Mallinckrodt <ajm@csupomona.edu>]

Kyle, 

It sounds to me like you are somehow trying to treat energy and amplitude as independent quantities.  Fundamentally, it comes down to this:  In the far field, the energy (per unit area) IS the amplitude squared.  Thus, since E ~1/r^2, A ~ 1/r.

John Mallinckrodt
Cal Poly Pomona

The amplitude squared IS the energy.
On Jun 27, 2011, at 6:31 AM, Kyle Forinash wrote:

> John;
>
> This has helped but I'm still confused. Even if energy (amplitude) were 
> constant we would expect energy per area to drop as 1/r^2 because the 
> sphere surface area is expanding. If the amplitude is also decreasing as 
> 1/r then isn't the energy (amplitude squared) per area decreasing as 1/r^4?