# Form factor for Proton

To find the charge distribution of proton , we study electron proton scattering and compute the form factor to find the cross section. The form factor comes out to be Fourier transform of charge distribution. It is then multiplied by the cross section calculated under assumption that proton is point particle. What I don't understand is why the form factor has to be Fourier transform of charge distribution. I don't want the derivation but some intuition.

• Essentially in the far-field you just need to sum up a wave originating from each point in the slit. If you describe each wave as an exponential $e^{-ikx}$ then you can add up these waves by integrating the $e^{-ikx}$ multiplied by the slit. This is exactly the Fourier transform of the slit, ignoring constants etc. – Chris Cundy Aug 6 '15 at 13:01