Ewald’s optical extinction theorem

Abstract

Abstract In his commentary on Ewald’s fundamental papers (1916a,b, 1917, 1937) in Chapter 11, Hellmut Juretschke draws attention to the elegant way in which P.P. Ewald solved the boundary problem for the propagation of electromagnetic (e.m.) waves in a crystal. He describes how by using a half-space (with a boundary) Ewald was able to show that the incident e.m. field (the field incident upon the crystal from outside) was extinguished inside the crystal and replaced by another e.m. field with different wave number. Similar considerations were independently developed more macroscopically by C.W. Oseen (1915) and the extinction process gained the name of the ‘extinction theorem’ (or the ‘optical extinction theorem’ in the sense of ‘optics’) of Ewald-Oseen. This chapter reanalyses the action of this ‘extinction theorem’ in an amorphous optical dielectric rather than a crystal and traces some of the subsequent history of the extinction theorem and its various applications in this context.