The Reflexion of X-Rays by Crystals

Abstract

Theory of Reflection of X-rays from a Point Source, by a Perfect Crystal.—The derivation of the expression for the total reflected energy as obtained by other physicists, is given in simpler form. It is shown that the reflected rays are parallel in the plane of incidence but diverge in the perpendicular plane. Making the simplifying assumption that no ray is reflected more than once from any plane of atoms and that the absorption by the crystal is negligible, expressions for the intensity at any point in the reflected beam are derived. It is shown that interference fringes are to be expected whose distance apart under ordinary circumstances may be of the order of 4 × ${10}^{-4\mathrm{}}$ cm. The error due to the above mentioned simplifying assumptions can be corrected by multiplying by the appropriate exponential factor.