# Single slit diffraction / wave propagation

I have a couple of questions about single slit diffraction. It's not a homework exercise - just a conceptual problem. Here it is (with some introductory comments)...

I understand that the diffraction pattern from a single slit is the modulus squared of the Fourier transform of the aperture. We have all seen the picture of the slit and the resulting |sinc|^2 profile. My question is in regards to what the position/location of these fringes mean in terms of spatial frequency. I'm wondering exactly what these spatial frequencies correspond to.

I'll have a go - Is it that the sum of plane waves having different spatial frequencies (defined by the diffraction pattern) will, when summed up, equal the object (aperture)?

If so, what spatial frequency does the first bright spot away from the central spot represent? Is the wave vector the addition of the original (defined by the incident propagation direction) and the displacement vector (defined by the transverse position along the diffraction pattern)? OR does the first bright spot simply represent the inclusion of a wave with spatial frequency defined by the displacement vector, i.e. a wave traveling perpendicular to the incident wave?

apologies for the long-windedness! :-)