. The Bell System technical journal . Powder method diffraction-rings obtained with X-rays and massesof small crystals of a nickel-iron alloy built on a cubic lattice. The rings are uni-formly dark for one sample because the crystals were oriented quite at random,while for the other there were certain preferred orientations and the rings arespotted. (R. M. Bozorth.) CONTEMPORARY ADVANCES IN PHYSICS 417 sum-of-squares (hx^ + h-r + /zs), their rings coincide. They appearas dark circles on a photographic film so placed as to coincide withsuch a sphere or such a plane, exposed and subsequently dev
. The Bell System technical journal . Powder method diffraction-rings obtained with X-rays and massesof small crystals of a nickel-iron alloy built on a cubic lattice. The rings are uni-formly dark for one sample because the crystals were oriented quite at random,while for the other there were certain preferred orientations and the rings arespotted. (R. M. Bozorth.) CONTEMPORARY ADVANCES IN PHYSICS 417 sum-of-squares (hx^ + h-r + /zs), their rings coincide. They appearas dark circles on a photographic film so placed as to coincide withsuch a sphere or such a plane, exposed and subsequently of these circles consists of the diffraction-spots with the appro-priate indices cast by the various crystals. If the crystals are few,one sees the individual spots (the ring looks ragged and spotty, like astar-cluster); if they are few and small the spots are hazy; if insteadof being turned at random they favor certain orientations, the circlesare not evenly dark all the way round. But these are matters forlater Fig. 19âPowder method diffraction-rings obtained with X-rays and a nickel-iron alloy. Like the alloys used in Figs. 17, 18, the crystals of this are built on acubic lattice but with a differently-shaped atom-group, whence the changed ap-pearance. (R.|[M. Bozorth.) If we measure the radii of the first few rings and calculate fromthem the values of (1 â cos $) for the corresponding cones (a simplematter of geometry) we should find that these stand to one anotheras 1 : 2 : 3 : 4 ⢠⢠âprovided, that is, that the lattice is cubic andthe incident waves are nearly monochromatic. This is verified byexperience for X-rays and electron-waves. The first ring consists ofspots having the indices (1, 0, 0) or (0, 1, 0) or (0, 0, 1); the indicesfor the second ring are (1, 1, 0) or (0, 1, 1) or (1, 0, 1), while thosefor the third are (1, 1, 1). The reader can easily guess the indices 418 BELL SYSTEM TECHNICAL JOURNAL which yield other small integer values f
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