Tyndall, John, 1820-1893 · New York : Appleton · leaf 96
than the tenth of a second, the wavy line of lightwill occupy for a moment the whole width of the screen.Instead of permitting the beam from the lamp to issuethrough a single aperture, it may be caused to issue throughtwo apertures, about half an inch asunder, thus project-ing two disks of light,… … place the two disks beside each other, on exciting the forkand moving, the mirror, we obtain a beautiful interlacingof the two sinuous lines, Fig. 24. Fig. 24.
Sound
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