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.

    54/318 (page 44)
    Now, through 0 let the lines-OB and OB' be drawn parallel respectively to SA and SA'; then will L'OI' =' 180° — L'OB — BOB* — B'OE; but L'OB 5= B'OE =z LIA =z 90° — LIN. Hence, L'OI' = 180° — 180° + 2 LIN — BOB'; or, calling the angle of incidence I, and the angle of minimum deviation D, D = 21 — Or, A T D + G and .. I = —g— Now, denoting the index of refraction by n, we have sin I _ _ ;' sin R •and hence, by substitution, . D 4 G sin —t;— . G sin — 2 To determine, therefore, the indices of refraction, we have only to measure the angle's D and G. 49. Determination of the indices of refraction.- § 1. Solids. The substance of which the index is sought, being wrought into the prismatic form, to measure the.refracting angle ASA' [Fig. 39', Plate IV], we fix the prism in a position such that its edges shall be perpendicular to the plane of n gra- duated circle; and with a telescope which revolves