I know this may sound like a homework question but it is not. I am having an argument with my science teacher and I was hoping you guys could help me prove her wrong. The argument goes as follows: My teacher says diffraction cannot take place if the opening is bigger than the wavelength of the wave. I say that diffraction can take place regardless whether the split is bigger or smaller than the wavelength, but diffraction cannot take place if the distance between the source of the wave and the split is smaller than the split. Please tell me if I am right and if you have any links to proof it, I would really appreciate it (the link is so that I can print proof from a reliable source to show my teacher).