An elementary treatise on optics / by I.W. Jackson.

  • Jackson, I. W. (Isaac Wilber), 1804-1877.
Date:
1867
Catalogue details

Licence: Public Domain Mark

Credit: An elementary treatise on optics / by I.W. Jackson. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

    102/318 (page 92)
    A few of the results of Fraunhofer's experiments are given in the following table.# INDICES OF REFRACTION FOR THE SEVEN FIXED LINES, B, C, D, ETC. OF THE SOLAR SPECTRUM. SUBSTANCES. B C D E F Gr H Water, 1.3309 1.3317 1.3336 1.3359 1.3378 1.3413 1.3442 Oil of turp. 1.4705 1.4715 1.4744 1.4781 1.4817 1.4882 1.4938 Cr'n. glass, 1.5258 1.5268 1.5296 1.5330 1.5361 1.5417 1.5466 Flint glass, 1.6277 1.6297 1.6350 1.6420 1.6483 1.6603 1.6711 We shall continue to use the terms indices of the mean and extreme rays, it being understood that by them we mean the indices of the rays correspond- ing to the appropriate fixed lines. 70. The dispersion of light, and the dispersive power of a medium. The separation of a beam of compound light into its elementary rays, considered in the preceding articles, is called the dispersion of light. The pro- perty by which a medium effects this dispersion is called the dispersive power of the medium. Different media possess different dispersive powers. To illustrate this principle, let ABC, A'B'C [Fig. 68] be two prisms, the first of flint, the second of crown glass; LI and LT two indefinitely small beams of white light, incident upon them, at the same angle; and IV, IR, TV, IE/, the extreme emergent rays. Then, 1st. When the refracting angles of the two prisms are equal, it is observed that both IB, and IV *'The indices given in the table, in Art. 49, are those of the yellowish green rays, it having been agreed to consider them as the mean rays of the spectrum.