Re: Wave Question

[romanza <romanza@MBOX3.SINGNET.COM.SG>]

----- Original Message -----
From: DEVARAKONDA VENKATA NARAYANA SARMA <narayana@HD1.DOT.NET.IN>
To: <PHYS-L@lists.nau.edu>
Sent: Saturday, September 11, 1999 4:23 PM
Subject: Re: Wave Question


> At 05:59 PM 9/10/99 -0700, you wrote:
> > You must look at the whole system. Energy is a system state function;
> > there is no reason to expect that it will be conserved locally. If you
> > consider the intensity which impinges on all the walls of the container
> > you will account for all of the energy radiated. After all, there are
> > also some places where the interference is destructive and the intensity
> > is nearly zero.
>
> Perhaps we can also say that the intensity should always be calculated
> from the resultant amplitude obtained by adding individual amplitudes
> giving due consideration to the phase and not by adding individual
> intensities.
> Intensity should be always via amplitude.
>
> regards,
>
> sarma.

Calculating from the amplitude is well-established. But I was pondering
where the "extra" energy came from, and this has also been answered
qualitatively --- by looking at the whole system, i.e. while the energy has
doubled at constructive points, the energy is lowered on other points. But
how do we prove it more convincingly, maybe mathematically?

romanza