**GOT IT** I don't normally ask for Physics help....but, uh, yea, so uh...

[beer]

Hint: The angle may be too large to use small
angle approximation.
Sound waves of frequency 586 Hz enter a
window 1:27 m wide. The window is in the
exact center of one wall of a theater 24 m by
12 m. The window is 12 m from the opposite
wall, along which is a row of seats occupied by
people. The theater is acoustically prepared
to prevent the refection of sound waves, and
the speed of sound is 330 m/s. Two people,
on each side of a line directly in front of the
window, in the row along the wall hear no
sound.
What minimum distance are they from each
other? Answer in units of m.

 

[Heisenberg]

Good problem. I'm not sure exactly how to do this, but it sounds similar to the diffraction of light waves through a slit. It's just going to take a good diagram and a bunch of trig. I'm guessing the answer is going to be some form of (n+1/2)*wavelength so that destructive interference occurs at both spots.

 

[beer]

Actually I got it. I had to use the book though since I didn't know the equations except for the small angle approximation...

The basic equation for single slit diffraction was sin(theta) = m*lamba/a, m = order of minima. a = appature width. Solve for theta = arcsin(lambda/a). The length of the room is 12m, 12tan(theta) is the distance from the center of the window to either observer, therefore the answer was 24tan(theta).

 

[Heisenberg]

Originally posted by: Elemental007
Actually I got it. I had to use the book though since I didn't know the equations except for the small angle approximation...

The basic equation for single slit diffraction was sin(theta) = m*lamba/a, m = order of minima. a = appature width. Solve for theta = arcsin(lambda/a). The length of the room is 12m, 12tan(theta) is the distance from the center of the window to either observer, therefore the answer was 24tan(theta).

Ohhhh sure, look up the equation for diffraction. Back in my day we had to derive it while we walked uphill both ways to school.

 

[beer]

Yea yea, and I solved it in my TI89. No trig tables or slide rules for me

 

[Heisenberg]

Originally posted by: Elemental007
Yea yea, and I solved it in my TI89. No trig tables or slide rules for me

/me shakes cane angrily and goes to take a nap