Heinrich Rubens
Heinrich Rubens (c1865-1922)
1922 Obituary[1]
"The Late Professor H. Rubens.— Professor Heinrich Rubens, who died recently in his fifty-seventh year, was best known for his systematic optical work, especially in the infra red region of. the spectrum which he extended very considerably by means of his “Rest-strahlen ” method. He observed'that certain crystallised minerals have a preferential reflection for very limited ranges of rays so that repeated reflections -would concentrate the rays of certain wave lengths^ the “remnant ” rays being almost free of other rays. Such minerals and salts are fluospar, rock salt, sylvin (potassium chloride) and potassium bromide. A further concentration he effected, partly in conjunction with R. W. Wood, of Baltimore, with the aid of quartz lenses which, he found, give images of the different rays, passing through slits, at different distances. In these various researches on the dispersion and absorption of light, the thermopile, which bears his name, and his armour-clad galvanometer proved very useful. Together with Hagen he had previously worked with the Reichsanstald, on the reflective power of metals. These researches, as well as those on black body radiations, and his determinations of dielectric constants, were of great importance in connection with the theory of radiation and absorption, and supplied valuable material for Planck when he was advancing the quantum theory. Rubens was director of the Physical Institute of Berlin University and was respected as an exact worker and teacher."