‎"EINSTEIN, A. - THE REFRACTIVE INDEX FOR X-RAYS.‎
‎Lassen sich Brechungsexponenten der Körper für Röntgenstrahlen experimentell ermitteln ? (+) Bemerkung zu E. Gehrckes Notiz ""Über den Áther"". (2 Papers).‎

‎Braunschweig, Friedr. Vieweg & Sohn, 1918. Contemp. full cloth. Spine gilt and with gilt lettering. In: ""Verhandlungen der Deutschen Physikalischen Gesellschaft im Jahre 1918."", 20. Jahrgang. V,280 pp, textillustr. (Entire volume offered). Einstein's papers: pp. 86-87 and p. 261. Clean and fine.‎

Reference : 47167

‎First printing of the paper in which Einstein provided the first description of the nature of the refractive index for X-rays, that it has an imaginary component, and showing that phase contrast effects are significant. 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.The second paper is Einstein's reply to Gehrcke's paper ""Über den Äther"" as printed in the offered volume pp. 165-169.Weil: 100 a.104 - Boni: 101.a. 102.The volume contains orher importent papers by MAX BORN, E. GOLDSTEIN, J. PETZOLDT, MAX BORN & A. LANDÉ, A. LANDÉ.‎