Notes on Standard Wave lengths spectographs, and spectrum tubes . ctra are observed near the normal to thegrating. Runge and Paschen used a lens with the slit at itsfocus filling the grating with parallel light. On account of absorp-tion and faults of achromatism in lenses, Fabry and Buisson 12recommended the use of a mirror with which to illuminate thegrating. Such an arrangement was installed in a basementlaboratory at this Bureau 13 in 1914 and has been in almost con-tinuous use ever since. In view of the fact that this type of 192 Scientific Papers of the Bureau of Standards [ gratin
Notes on Standard Wave lengths spectographs, and spectrum tubes . ctra are observed near the normal to thegrating. Runge and Paschen used a lens with the slit at itsfocus filling the grating with parallel light. On account of absorp-tion and faults of achromatism in lenses, Fabry and Buisson 12recommended the use of a mirror with which to illuminate thegrating. Such an arrangement was installed in a basementlaboratory at this Bureau 13 in 1914 and has been in almost con-tinuous use ever since. In view of the fact that this type of 192 Scientific Papers of the Bureau of Standards [ grating mounting has many excellent features but has never beendescribed in detail, we have considered it worth while to show aplan of our instrument (Fig. 2), reproduce our working drawingsof its parts (Figs. 3, 4, and 5), and add a few notes on its charac-teristics and performance. The light from a source whose image is focussed on the slit 5falls upon a concave mirror M (of speculum metal), which sendsa parallel beam of light to the grating G. The slit and grating.
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernatio, bookyear1922
