The Diffraction of Cathode Rays by Thin Films of Platinum

Abstract

IN a letter to NATURE of June 18, Mr. Reid and I described the rings formed when a beam of cathode rays was sent at normal incidence through a thin film of celluloid and struck a photograph plate placed some distance behind the film. These were attributed to a diffraction of the cathode rays by the film, the cathode rays behaving as waves of wave-length h/mv according to do Broglie's theory of wave mechanics, and regularities in the structure of the film, or in the size of the molecules, making it behave as a kind of diffraction grating. In a paper now awaiting publication by the Royal Society, this work has been confirmed and extended to films of gold, aluminium, and of an unknown (probably organic) substance. In particular, the relation that the size of the rings is in all cases inversely as the momentum of the cathode rays is fully confirmed, and the number and size of the rings correspond remarkably with what is to be expected from the known crystalline structure of gold and aluminium, using de Broglie's expression for the wave- length of the cathode rays.