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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 10, Iss. 2 — Feb. 1, 1925
  • pp: 169–235


JOSA, Vol. 10, Issue 2, pp. 169-235 (1925)

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, "SPECTROPHOTOMETRY," J. Opt. Soc. Am. 10, 169-235 (1925)

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  1. Letter of Feb. 7, 1923, Pres. L. T. Troland to chairmen of Progress Committees.
  2. The relation between spectrophotometry and colorimetry has been treated in the Reports of the Colorimetry Committee (1 ;4). The fundamental nature of color specification based upon spectrophotometric data is readily granted by experts in color (4, p. 574; 119, p. 700; 120, pp. 73–75; 121, p. 41; 123, p. 42). The reasons that colorimeters and colorimetric methods have, nevertheless, been so extensively used is that they are often simpler and speedier of application and the results may be more readily interpreted as color (Cf. Sec. II-5 and 6, and Sec. VII-1).
  3. The word light has been commonly used to designate the product of radiant power by visibility as well as radiant energy by visibility. Indeed, in this report, where light is considered as the adequate stimulus of color, the word is used in this sense. The unit employed in the designation of absolute visibility, the lumen per watt, is also in accord with this usage. Nevertheless, it seems best to define light primarily as above, considering it as the luminous entity which is emitted, absorbed, reflected, etc., analogous to radiant energy.
  4. Instruments not designed primarily for spectrophotometry often have the ocular slit St omitted. In such cases the eye piece usually carries an adjustable diaphragm which may be made to serve as a slit, or may carry cross hairs by which the location in the spectrum is determined.
  5. In prism instruments a curvature of the spectral line may be noted, especially if Sc is viewed at full length. Only the light from the center of Sc undergoes true minimum deviation. The central part of the line should, of course, be made parallel to St. It will also be found that the complete spectrum cannot be brought into exact focus by any single adjustment. The lenses for the usual visual instrument are achromatised for the range 486–656 mµ (C to F). If the instrument is focussed upon some line in this range, preferably in the yellow, it will probably be in focus at all wave lengths not only in this range but also throughout the red, but towards the shorter wave lengths the parallax between St and the spectral line will become increasingly noticeable.
  6. Adam Hilger, Ltd., 75a Camden Road, London.
  7. The Gaertner Scientific Corp., 1201 Wrightwood Ave., Chicago, Ill.
  8. Bausch and Lomb Opt. Co., Rochester, N. Y.
  9. Schmidt & Haensch, Berlin.
  10. Keuffel and Esser Co., Hoboken, N. J.
  11. Clear white fluorite will transmit much farther into the ultra-violet than quartz, but is extremely rare.
  12. Adam Hilger, Ltd., 75a Camden Road, London.
  13. This will be more certainly insured if the two points considered are on closely adjacent parts of the same plate.
  14. Adam Hilger, Ltd., 75a Camden Road, London.
  15. P/P′ = (s′/S)n, where P and P′ are two radiant powers incident for exposure times s and s′, respectively, of such length that equal density results in the two cases. The exponent n is less than unity (for continuous exposures).
  16. If a plate is exposed to a constant radiant power for time s (continuous) and then exposed for the same effective time s, made intermittent by means of a rotating sector, the density in the second case is less than that in the first.
  17. The most sensitive cells have the metal in the hydride form and contain some inert gas.
  18. Keuffel and Esser Co., Hoboken, N. J.
  19. Frehafer and Snow, Tables and Graphs for Facilitating the Computation of Spectral Energy Distribution by Planck's Formula. Bur. Stand. Misc. Pub. No. 56.
  20. Cf. also M. Luckiesh, The Equality-point in Spectral Energy- and Luminosity-Distribution Curves of Illuminants. Jour. Frank. Inst., 183, p. 633; 1917.

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