X-rays are electromagnetic waves of very short wavelength. The wave nature of X-rays is not confirmed by diffraction experiment, because a grating of about 40 million ruling per cm is required for diffraction experiment. The preparation of such a grating is highly impossible. At the same time, crystallographers believed that atoms in crystals are regularly arranged with an interatomic distance of about 10-8 cm. The wavelength of X-rays is, also, in the order of 10-8 cm. Based on this, Laue suggested that crystal can be used as a three dimensional diffraction grating for X-rays. This suggestion is carried out successfully by Laue in his experiment using zinc sulphide crystal. The photograph obtained is known as Laue diffraction pattern.
The Laue experiment confirmed the wave nature of X-rays and also established the fact that atoms or ions in crystals are arranged in regular three dimensional lattice. Though Laue diffraction pattern gives more information about the symmetry of crystals, the interpretation of the pattern seems to be difficult.
