Ultra-violet reflecting power of aluminum and several other metals

Abstract

In this paper data are presented on the ultra-violet reflecting power of alumi-num, duralumin, tin, and rhodium. The data on aluminum are of special interest in connection with the use of this metal in reflectors of therapeutic lamps. The results of this investigation show that the ultra-violet reflecting power of aluminum compares favorably with that of chromium (previous investigation, RP39), increasing in reflecting power from about 50 per cent at 300 m/x to 75 per cent at 550 mju. In the visible spectrum, the reflectivity is higher than that of chromium. The ultra-violet spectral reflection of duralumin is similar to that of alumi-num. Tin has a fairly high reflecting power and may be useful in certain types of echelette gratings. Mirrors of rhodium are best prepared by cathode sputter-ing. The reflectivity observed on a polished regulus of rhodium increases from about 30 per cent at 260 mju to 45 per cent at 365 m/i.