1. In satisfying the Bragg's law, [tex]n\lambda=2d\sin\theta[/tex], n is typically assumed to be one, which explains why we see only one peak for a particular plane (say  plane for silicon). But I really don't see why n=2 should not appear as an equally strong peak..? 2. Is the Fourier transform effect of X-ray scattering comparable to that of a Fraunhoffer diffraction by multiple slits? 3. In calculating the Fourier transform of the original lattice, how is the origin of the r vectors determined? Or it doesn't matter? Thanks!