Geometrical optics / by Archibald Stanley Percival.

  • Percival, A. S. (Archibald Stanley), 1862-
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: Geometrical optics / by Archibald Stanley Percival. Source: Wellcome Collection.

    77/148 (page 65)
    ' REFRACTION AT A SPHERICAL SURFACE 65 and primary focal lines, but the lateral surfaces of the refracted beam will now intersect in the secondary focal line at F, before the final edge of the sphenoid is formed at F,, the primary focal line. If OP were greater than pu(F;P), F,P would be greater than F,P (see Appendix, p. 116); in such a case the refracted beam would take exactly the form - represented in Fig. 15, The formule for the lengths F,P or 2, and for FoP or %%, when the source of light O is at a distance OP or wu, will be merely stated in this place— pcos*¢ cos*d mw 1 V4 ear Naar us The proof of these formule will be found in the Appendix, pp. 114-116. Conversion of Formule of Refraction into those of Reflec- tion.—On p. 35 it was stated that sare e (or HY = a. 1.e. the sin @ Mo) Ve ratio of the speed of light in the first medium to its speed in the second medium. Now, when reflection occurs at a sur- face, it is clear that the speed of the light is unchanged in absolute amount, for it is in the same medium, but its direc- tion is reversed; in other words, the sign is changed, so that F