. The principles underlying radio communication . ity and Magnetism for Advanced Stu-dents, 2d ed. (1916), pp. 423-429, from which Fig. 158 is taken. 296 ELECTROMAGNETIC WAVES. ends get to the gap before the middle portion, as shown in , they will cross as before, and soon thereafter we willhave the loop formed as in Fig. 158-iv. Now, at some timy asthe ends continue to go up, this loop will break, forming twoparts m and n, as shown in Fig. 158-v. This is because at thatmoment the angle of intersection becomes so acute that eachpart of the line will be moving parallel to its length,
. The principles underlying radio communication . ity and Magnetism for Advanced Stu-dents, 2d ed. (1916), pp. 423-429, from which Fig. 158 is taken. 296 ELECTROMAGNETIC WAVES. ends get to the gap before the middle portion, as shown in , they will cross as before, and soon thereafter we willhave the loop formed as in Fig. 158-iv. Now, at some timy asthe ends continue to go up, this loop will break, forming twoparts m and n, as shown in Fig. 158-v. This is because at thatmoment the angle of intersection becomes so acute that eachpart of the line will be moving parallel to its length, in whichcase neither half will have any magnetic field and, consequently,no momentum to carry them by each other. The process goeson as shown in Figs. 158-vi, 158-vii, and 15S-viii, the last of whichshows the state of things w^hen one half oscillation has been com-pleted and the charges on the oscillator have been reversed insign. A cylindrical sheet of lines of force has then been de-tached from the oscillator and is traveling outward. At this. in r^a. 135 ElecThic field of aHerTjiarv OjcilUtordtdifferent nvomeftTa duriiKO<a Kdilf cycle moment those lines left attached to the oscillator have beenstretched as far as their momentum can carry them, and theybegin to contract again and repeat the process, provided thegap is still conducting. In the next half wave length anothercylindrical sheet of lines of force will be snapped off, so tospeak, and the process will continue until the energj^ lost asheat in the oscillator has exhausted the supply of lines whichremain attached to it. These cylindrical sheets, as they spreadout, become more and more nearly plane, the plane being per-pendicular to the motion away from the oscillator. During the RADIATION 297 process shown in Figs. 158-ii to 158-vii—tliat is, while the currentin the oscillator is flowing upw^ard—the motion of the electriclines of force generate magnetic lines (not shown), which formcircles around the oscillator
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