. Various photo-electrical investigations. gh photo-electrical sensitivity throughout the visible spectrum, with amaximum at These two cells are interesting in showing the shifting of thejnaximum of the spectrophoto-electrical reaction toward the long -^ B. S. Sci. Papers, IC, p. 600; 1020. Case, Phys. Rev. (2), 7, p. 398; 1921. Coblent:] Photo-Electrical Investigations. 603 wave lengths with increase in atomic weight, as previously ob-served in the alkali metals. Curve C gives the spectrophoto-electrical reaction of cell , consisting of barium and 5 per cent strontium. The prese
. Various photo-electrical investigations. gh photo-electrical sensitivity throughout the visible spectrum, with amaximum at These two cells are interesting in showing the shifting of thejnaximum of the spectrophoto-electrical reaction toward the long -^ B. S. Sci. Papers, IC, p. 600; 1020. Case, Phys. Rev. (2), 7, p. 398; 1921. Coblent:] Photo-Electrical Investigations. 603 wave lengths with increase in atomic weight, as previously ob-served in the alkali metals. Curve C gives the spectrophoto-electrical reaction of cell , consisting of barium and 5 per cent strontium. The presenceof the strontium produces a relatively steeper curve, with a weakerreaction in the red than obtains in the pure barium cell. In the manufacture of these cells the object in view is the pro-duction of a device which can be used as a physical photometerfor daylight recording, etc. For this purpose the photo-electriccell is to be covered with a suitable (yellow glass) screen, whichreduces the sensitivity in the violet end of the •3 /f- .5 j& .V Fig. 8.—Specirophoto-elecirical reaction curves of Cases new Ba and Srphoto-electrical cells. In Figure 8 the dotted curve, D, is the visibility curve of theaverage eye. The points marked with the crosses (X X X) givethe spectropho to-electrical reaction of barium cell No. 380 whencovered with a brownish-yellow screen. The agreement betweenthe photo-electrical response curve and the visibility curve isremarkably close, showing that the production of an exact matchis merely a matter of patience in making up a suitable screen. X. SPECTROPHOTO-ELECTRICAL SENSITIVITY OF CUPROUSOXIDE AND OF LEAD-ANTIMONY SULPHIDE. These substances were kindly supplied by the Case Research Laboratory. 1. CUPROUS OXIDE. In Figure 9 is given the spectrophoto-electrical reaction curve ofa sample of cuprous oxide, CujO, in the form of a single semi- 6o4 Scientific Papers of the Bureau of Standards. [Vol. 18 translucent red crystal (size about 10 by
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Keywords: ., bookauthorcoblentz, bookcentury1900, bookdecade1920, bookyear1922
