Ocular refraction and the shadow test . y axis L E. The conjugate foci of E L and F P lo-cates the image of the point L at L; in the same manner locate theimage of M at M, etc. When the object lies wholly to one side of theprinciple axis the image is upon the other. O C U L A K R E F R A C T I O N. In figure 21 the object L M is situated between the principlefocus P and the vertex D An incident ray L E parallel to theprinciple axis C D is reflected through the principle focus P; a second-ary axis C L meets A B at G and a ray from L to G is reflectedthrough C; the reflected rays G C and E P are
Ocular refraction and the shadow test . y axis L E. The conjugate foci of E L and F P lo-cates the image of the point L at L; in the same manner locate theimage of M at M, etc. When the object lies wholly to one side of theprinciple axis the image is upon the other. O C U L A K R E F R A C T I O N. In figure 21 the object L M is situated between the principlefocus P and the vertex D An incident ray L E parallel to theprinciple axis C D is reflected through the principle focus P; a second-ary axis C L meets A B at G and a ray from L to G is reflectedthrough C; the reflected rays G C and E P are divergent and, there-fore, cannot meet; they have but a virtual focus which is located byextending them back of the mirror where they meet at the point L;the point M is found in the same way, and L M represents the vir-tual image of L M. Figure 22 shows at a glance the characteristics of images formedof objects in different positions with regard to a concave mirror; thedotted lines connect each object and its image. The- image of L is. elween principle: ol)jecl, L M; image L M; principle focus, P. at L, is inverted, real and magnified; the image of L is at L, is in-verted, real and smaller, the image of N is at N, is erect, virtual andslightly magnified; while the image of M is at M, is erect, virtual andgreatly magnified. The centre of curvature is represented at C, theprincipal focus at P, and the mirror at A B. Figure 23 illustrates the formation of the image by a convexmirror. The object is at L M, the mirror is A B. To locate the im-age of the point L, draw the path of a ray from L through C; anotherfrom L parallel to C D, construct the angles of incidence L F F andthe angle of reflection K F F; by extending K F back of the mirroras a straight line, it meets L C at L. Anutner ray from L to E isreflected to H, L E E being equal to H E E; extending fl E backof the mirror as a straight line it also passes through L, which is,therefore, the virtual focus for all rays from the
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Keywords: ., bookcentury1900, bookdecade1900, bookidocularrefrac, bookyear1903
