Optics, Diffraction Homework: Intensity Expression on Far Screen

[fluidistic]

Homework Statement

On a screen there's a square aperture (hole) whose sides are 2a lengthy. We put a square of lengths a in the center of the hole. We illuminate the aperture with an He-Ne laser ([tex]\lambda =632.8 nm[/tex]). We put a screen far from the screen with the square aperture, so that we can deal with Fraunhofer's diffraction.
1)Give the expression of the intensity on the far screen.
2)I'm not sure of the other questions but I think they were asking more or less the ratio of the intensities of the first 4 maximae or so.

Homework Equations

Not sure.

The Attempt at a Solution

Totally stuck on this. Of course I don't except an answer to the question here, rather what method should I investigate. I have Hecht's book on Optics at my disposition but I find it very hard to learn the diffraction and Fourier Optics chapters. I have no knowledge on Fourier (anti) transforms, but I have all the prerequisites to learn it.
Do you have any book/website that can help me for this problem?
Also I'd like to "play" and solve similar problems like what happens if I have a circle as a hole in the screen and I put a square inside of it... a triangle, etc.

 

[BigJDubs]

I've checked everything I could find on the web, but I can't seem to find what I'm looking for. Do you have any idea? Thanks a lot in advance!