Diffraction studies on a polycrystalline Al sample using X-rays gives the smallest diffrac...

Diffraction studies on a polycrystalline Al sample using X-rays gives the smallest diffraction angle (2θ) of 29.5° corresponding to diffraction from the (111) planes.  The lattice parameter a of Al (FCC), is 0.405 nm.  If we wish to obtain the same diffraction pattern (same angle) using an electron beam, what should be the voltage needed to accelerate the electron beam? Note that the interplanar separation d for planes (h,k,l) and the lattice parameter a for cubic crystals are related by

  d = a / [h2+k2+l2]1/2