The microscope; an introduction to microscopic methods and to histology . ain sufficient refraction to make the combination serve for theproduction of images. (See also the discussion under apochromatic objectives \ 22 ) Probably no higher technical skill is used in any art than is requisite in thepreparation of microscopical objectives, oculars and illuminators. Figs. 14 and 15. 14. Convex lensshowing the position of the object (A-B)outside the principal focus (E), andthe course of the rays in the formationof real images. To avoid confusion therays are drawn from only one point. A B. Object o
The microscope; an introduction to microscopic methods and to histology . ain sufficient refraction to make the combination serve for theproduction of images. (See also the discussion under apochromatic objectives \ 22 ) Probably no higher technical skill is used in any art than is requisite in thepreparation of microscopical objectives, oculars and illuminators. Figs. 14 and 15. 14. Convex lensshowing the position of the object (A-B)outside the principal focus (E), andthe course of the rays in the formationof real images. To avoid confusion therays are drawn from only one point. A B. Object outside the principalfocus. B A. Real, enlarged imageon the opposite side of the lens. Axis. Principal optic axis. 1,2, after traversing the lens. Theyare converging, and consequently forma real image. The dotted line and theline (2) give the direction of the rays asif unaffected-by the lens. (E). Theprincipal focus. Fig. 15.—Convex lens, showing theposition of the object {A B) within theprincipal focus and the course of raysin the formation of a virtual 14 15 A B. The object placed between the lens and its focus; A B virtual imageformed by tracing the rays backward. It appears on the same side of the lens asthe object, and is erect (\ 11). Axis. The principal optic axis of the lens. F. The principal focus. 1, 2, 3. Rays from the point B of the object. They are diverging after trav-ersing the lens, but not so diveigent as if no lens were present, as is shown by the MICROSCOPE AND ACCESSORIES [CH. I dotted tines. Ray (/) traverses the center of the lens, and is therefore not is a secondary axis {\ 5). \ 10. Geometrical Construction of Images.—As shown in Figs. 14-15, for thedetermination of any point of an image, or the image being known, to determinethe corresponding part of the object, it is necessary to know the position of theprincipal focus (and there is one on each side of the lens, § 6), and the opticalcenter (Figs. 1-9 of the lens). Then a
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