. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. 314 PHI 'SIOLOG1CA L PHYSICS. [Chap. XXV. it. Thus, in the case of ray 1, the refraction on entering the lens is towards the normal n, on leaving, because the ray passes from a rarer to a denser medium, the bending is away from the normal n', the result of both refractions being to direct the ray towards F, the principal Tig. Focus of J°CUS- Jhe a^ f°rUied a Convex Lens. by rays irom the circumference of the len
. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. 314 PHI 'SIOLOG1CA L PHYSICS. [Chap. XXV. it. Thus, in the case of ray 1, the refraction on entering the lens is towards the normal n, on leaving, because the ray passes from a rarer to a denser medium, the bending is away from the normal n', the result of both refractions being to direct the ray towards F, the principal Tig. Focus of J°CUS- Jhe a^ f°rUied a Convex Lens. by rays irom the circumference of the lens and the principal focus is the aperture of the lens. On the other hand, if the luminous body be at F, the rays after emergence from the lens will be parallel to one another. 2. Let the rays diverge from a luminous point, and fall on a convex lens, they are no longer focussed at the principal focus. Suppose, as in Fig. 141, the rays proceed from a pointy* which is farther from the lens than the focal distance. After refraction they meet in a point f outside of the principal Fig. Foci of a Convex focus F. Or if the Lens, luminous point be at/'', the refracted rays will meet &tf. Because of the re- lation thus existing between f and f, they are called CONJUGATE FOCI. That is, f is the conjugate focus of /"', and/' of/'. Just as in the case of mirrors, as/" comes more and more nearly to be at the focal dis- tance from the lens its conjugate focus f moves farther and farther off, till if f coincide with the focal distance, the emergent rays will be parallel, and there will be no conjugate focus. Again, as y moves farther and farther from the focal distance its conjugate focus. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original M'Gregor-Robertson, J. (Joseph), 1858-1925. Philadel
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