Notes on Standard Wave lengths spectographs, and spectrum tubes . in sharp and are susceptible of accurate measure-ment. The instrument has been used very successfully in the spectralregion for which it was designed. Furthermore, it has been 7 B. S. Bull., 14, p. 765; 1918. 8 Ann. d. Phys., 51, p. uS; 1916. • B. S. Bull., 14, p. 710; 1918. 190 Scientific Papers of the Bureau of Standards [ found to perform satisfactorily when used to compare the spectraof the rare gases throughout the region 2600 A to 8000 A with thecadmium red line. For use in the visible spectrum the plateholder is set
Notes on Standard Wave lengths spectographs, and spectrum tubes . in sharp and are susceptible of accurate measure-ment. The instrument has been used very successfully in the spectralregion for which it was designed. Furthermore, it has been 7 B. S. Bull., 14, p. 765; 1918. 8 Ann. d. Phys., 51, p. uS; 1916. • B. S. Bull., 14, p. 710; 1918. 190 Scientific Papers of the Bureau of Standards [ found to perform satisfactorily when used to compare the spectraof the rare gases throughout the region 2600 A to 8000 A with thecadmium red line. For use in the visible spectrum the plateholder is set at an angle of about 50 degrees to the axis of thecamera. With this setting the definition is fair throughout, yetthe blue and green are not in perfect focus when the red (6438 A)and ultra-violet (3200 A) are both sharp. For wave length 2500 A the focal length of the collimator is1000 mm, that of the camera is 800 mm. Both have 50 mm ofclear aperture. Each lens has one element of right-handed andone of left-handed quartz of equal median thickness. The camera. Fig. i.—Quartz rock salt spectrograph, showing optical system of quartz and rock salt re indicated, full line position for ultra-violet and dotted line position lens has no rock salt element. The plane plate in the collimatorlens serves the double purpose of protecting the rock salt andcounteracting the optical rotation of the other quartz element. The radii and thicknesses of the lenses are as follows, beginningon the side toward the slit: Collimator lens: 1 [ right-handed quartz, thickness = co ; plane J & ? r3= +2055 mm; convex 1 rock salt, thickness at center mm; r4= —544 mm; concave J separation at center mm. r5= +; convex 1 left-handed quartz, thickness at center r8=+684 mm; convex J mm. ri= + 931 mm; convexr2= —24200 mm; concave *f£s] Spectroscopic Notes 191 Camera lens: right-handed quartz, thickness at cen-ter mm; separation at mm. r3= + 5°6 mm; convex lleft-han
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernatio, bookyear1922
