Lassen sich Brechungsexponenten der Körper für Röntgenstrahlen experimentell ermitteln? (p. 86-88, Weil 104) WITH Bemerkung zu E. Gehrckes Notiz Über den Áther (p. 265, Weil 100) in Verhandlungen der Deutschen Physikalischen Gesellschaft, Jg. 20-21, 1918-19

Braunschweig: Druck und Vieweg. 1st Edition. FIRST EDITION (FULL VOLUME) OF THE PAPER IN WHICH EINSTEIN PROVIDES THE FIRST DESCRIPTION OF THE NATURE OF THE REFRACTIVE INDEX FOR X-RAYS, here clearly demonstrating that phase contrast effects are significant.

"Inspired by the presence of fringes at the edges of objects in early X-ray images and by considerations of optical dispersion theory, Einstein suggested in 1918 that the real part of the index of refraction for X-rays in matter is slightly less than unity. This was confirmed in 1924 by Larsson et al. in measurements of wavelength-dependent refraction of X-rays by a prism" (Hornberger, Quantitative Amplitude, 1). "A century later, most x-ray microscopy and nearly all medical imaging remains based on absorption contrast, even though phase contrast offers orders of magnitude improvements in contrast and reduced radiation exposure at multi-keV x-ray energies"(ResearchGate, November 2015). Weil 104. Note that we offer this paper separately in its original printed wraps.

ALSO INCLUDED: Einstein's reply to Gehrcke's paper "Über den Äther" (also present in this volume, pp. 165-169).

ALSO INCLUDED: Papers by E. Goldstein, A. Landé, Max Born, and J. Petzoldt. CONDITION & DETAILS: Braunschweig: Druck und Vieweg. Full volume. Complete. 4to (9.25 x 6.25 inches; 225 x 150mm). Ex-libris with armorial bookplate on the front pastedown. Bound in brown cloth, rubbed at the edges; the cloth has torn at the spine and has been re-glued. Clean throughout. Good +.