Elements of natural philosophy (Volume 2-3) . Illustration ; To illustrate : let parallel rays be received by the lensA ; its action alone would be, to spread the differentcolors over the space VE, whose central point m, is dis-tant from A, 33 units of measure, (say inches), the violetbeing at V, and the red at R\ the action of the lens B,alone would be, to disperse the rays as though they pro-ceeded from different points of the line V B\ whose Explanation ofcentral point m, is distant from B, 50 inches, the violet ^JJ^J^appearing to proceed from V\ and the red from R\ and theeffect of their u
Elements of natural philosophy (Volume 2-3) . Illustration ; To illustrate : let parallel rays be received by the lensA ; its action alone would be, to spread the differentcolors over the space VE, whose central point m, is dis-tant from A, 33 units of measure, (say inches), the violetbeing at V, and the red at R\ the action of the lens B,alone would be, to disperse the rays as though they pro-ceeded from different points of the line V B\ whose Explanation ofcentral point m, is distant from B, 50 inches, the violet ^JJ^J^appearing to proceed from V\ and the red from R\ and theeffect of their united action would be, to concentrate thered and violet at F, whose distance from the lens isequal to the value of F, deduced from the formula 1 -| 1 Example; 1 _ _ j - = — inches. 2T - 33 ^ 50 97 , 06 308 NATURAL PHILOSOPHY. Point in which q\*red and violetwould be united; F = — 97 , 06 inches. Geometricalillustration ; Fig. V J£--jff why the otter Now, any one of the colors, orange for example, at ^iLiT0beDOt ^ *n ^e sPace ^ ^ which is thrown by theconcentrated in convex lens in advance of the centre m, and the same the same point; goXqv ^ gr ^ ^ gpace -pr, ^ which is thlWn by the concave lens behind the centre m\ will, it is obvious, beunited with the violet and red at F, by the joint actionof both lenses ; and the same would be true of any othercolor, but for the irrationality of dispersion of the me-dia of which these lenses are composed, which prevents it,and hence an image formed by such a combination oflenses will be fringed with color; the colors of the fringeconstituting what is called a secondary spectrum. Anadditional lens is sometimes introduced to complete theachromaticity of this arrangement. Secondaryspectrum. Substanceswhich fulfil theconditions forperfectachromaticity; § 120. If two lenses, constructed of media betweenwhich there is no irrationality of dispersion, be unitedaccording to
Size: 2897px × 863px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectmechanics, booksubjectopticsandphoto
