interference question

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

I can't really follow with your argument, while qualittaively I understood
what your meant totally.
The average intensity is 2a^2, but for individual wave, the average
intensity is only (a^2)/2 (averaging cos^2 for each), and hence the total
average intensity of the two waves is a^2.
Can you pls show me step-by-step how you arrive at the conclusion that
energy is conserved. thanks

romanza

----- Original Message -----
From: Michael Moloney <moloney@NEXTWORK.ROSE-HULMAN.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Saturday, September 11, 1999 8:43 AM
Subject: interference question


> The point of constructive interference has intensity 4A^2.   But you can
find another spot
> where the intensity is zero.  Does energy conversion hold up?  Yes it
does, and one nice
> way to see it is in the distant interference pattern of two very narrow
slits.
> Very far from the slits along their perpendicular bisector the intensity
is 4A^2. At other
> angles very far from the slits (assuming equal amplitudes A due to each
slit) the intensity
> depends on the cosine squared of half the phase difference between the
waves. You find
> out that the average intensity is 2A^2 when all is said and done, just
like you expect from
> energy conservation.
>
> Mike
>
>
> Mike Moloney, Dept of Physics & Applied Optics, Rose-Hulman Institute of
Technology
> (812) 877 8302    http://www.rose-hulman.edu/~moloney