Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'' (1912)
Barrows, William Edward, 1878-1960 · New York ; London : McGraw-Hill Book Co. · leaf 96
oduces no appreciablechange in the observed deviation from the law. In construction the disk can be made in several different forms.The simplest method of obtaining various ranges by means of thedisk is obviously to make a set of disks from some thin materialas sheet metal or fiber board having… … Fig. 24.—The sectored disk. It is obvious that a disk, the openings of which could be variedwithout stopping the motor and changing disks, would be desir-able. Such a device is shown in Fig. 24. There are two disks,D and D, which may be moved relative to each other about thesame axis. Both are…
Light · Photometry · Electric lighting
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