I'm doing past papers for my exam on Wednesday, and I've come to a question I'm stuck on.
So, you have x rays of $\lambda = 0.25\,\mathrm{nm}$ incident on a cubic unit cell with lattice lattice constant $a = 0.286\,\mathrm{nm}$.
The miller indicies are (101), (022), (103) and (022).
We're supposed to say which of these will give Bragg diffraction.
So, I figure calculate inter-planar spacing for these, using $d=\frac{a}{\sqrt{(h^2+k^2+l^2)}}$ but this gives answers smaller than $\lambda$.
I had thought lambda would have to be smaller to give diffraction
Thanks