. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 752 BELL SYSTEM TECHNICAL JOURNAL Imagine, at the outset, a pair of perfectly plane and parallel mirrors, onto which wave-trains of extended plane wave-fronts are falling from every direction. The mirrors must of course be semi-transparent, so that part of the light which falls first upon one—say, the upper— is reflected from it at once, and part goes on to meet and be reflected by the lower. Thus (as Fig. 3 shows more clearly than words) the. Fig. 3. mirrors form out
. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 752 BELL SYSTEM TECHNICAL JOURNAL Imagine, at the outset, a pair of perfectly plane and parallel mirrors, onto which wave-trains of extended plane wave-fronts are falling from every direction. The mirrors must of course be semi-transparent, so that part of the light which falls first upon one—say, the upper— is reflected from it at once, and part goes on to meet and be reflected by the lower. Thus (as Fig. 3 shows more clearly than words) the. Fig. 3. mirrors form out of each incident wave-train a first and a second reflected beam, which travel back through the space above the mirrors in the same direction, making according to the law of reflection the same angle i with the normal as the incident wave-train did. In truth there are not merely two reflected beams derived from each incident one, but an infinity thereof, owing to the multiple reflections which are indicated in the sketch. We need not however (as I shall presently show) take account of more than two; by combining the second re- flected beam with the first we can predict the most important features of the interference. It is necessary to be somewhat more precise about the nature of the mirrors. As good an example as any to begin with is that of the "thin plate"^—a slab of some transparent substance, glass for instance, embedded in a transparent medium which I will take to be empty space. The mirrors, then, are the upper and lower sides of the plate. Denote by /i the ratio of the speeds of light in the environing medium and in the substance of the plate, by i the angle of incidence of any wave-train and by r the angle of refraction of its transmitted part; then as heretofore we have s\m = IX sm r. (16). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illus
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
