. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. hertz's researches on electrical waves. 201 from the contral circle, and iu consequeuce is half a period behiud the l^hase which would be at the poiut if an inliuiresiinal portion of the center alone acted. For the effect of each ring can be considered as destroyed by half the effect of its two neighbors, and thus half the. Fig. 7. effect of the central circle is left uncompensated. But the distance of the edge of this circle is half a wave
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. hertz's researches on electrical waves. 201 from the contral circle, and iu consequeuce is half a period behiud the l^hase which would be at the poiut if an inliuiresiinal portion of the center alone acted. For the effect of each ring can be considered as destroyed by half the effect of its two neighbors, and thus half the. Fig. 7. effect of the central circle is left uncompensated. But the distance of the edge of this circle is half a wave-length farther from the point than its center is, so that the resultant phase at tbe point will be be- hind that due to the center, but in front of that due to the edge, which effect would be half a period behind that arising from the center. Taking the mean between them, the resultant phase then at the poiut is a quarter of a period* behind what it would be if the center alone acted. Thus it was that the reflection from the small sheet of zinc differed from what I had expected it to be. Experiment showing pliasc of secondary irares.—To experimentally test this, the small sheet of zinc was used as reflector in the Hertzian exjjeriment of looi)s and nodes. Employing the circular resonator, the position of interference was found to have shifted out from 17 to over 24 centimeters, which nearly corresponds to an acceleration of phase of a quarter of a period, the wave going in all nearly a quarter of a wave-length farther, and nevertheless being still only half a period behind the phase on starting. The farthest out the loop could be is centimeters : to obtain this would require an indefinitely small re- flector. Of course, when the resonator was close in to the sheet, no cliange of phase was found to occur, the sheet being then i)ractically infinite. Another interesting observation was made. A long sheet of zinc, 30 centimeters wide, was found to act similarly to the sheet
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