Show that the general direction [ hkl ] in a cubic crystal is normal to the planes with Miller indices (hkl). Is the same true in general for an orthorhombic crystal?
Show that the spacing d of the (hkl) set of planes in a cubic crystal with lattice parameter a is:
d = (a)/(h^2 + k^2 +l^2)^(1/2)
What is the generalization of this formula for an orthorhombic crystal?