Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . violet ray, as the most refrangible Fig. 28. one, is refracted towards V, and the red one, as the kast re- y nfrangible, is refracted towards E, and other colored rays fill out Tthe space between Fand R in the order of their rofrangibility. ~This is known as dispersion. The dispersion of refracting me-dia is measured by the length of the spectrum which they pro-duce. Flint glass has more dispersive power than crown glass,because the spectrum which it produces is
Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . violet ray, as the most refrangible Fig. 28. one, is refracted towards V, and the red one, as the kast re- y nfrangible, is refracted towards E, and other colored rays fill out Tthe space between Fand R in the order of their rofrangibility. ~This is known as dispersion. The dispersion of refracting me-dia is measured by the length of the spectrum which they pro-duce. Flint glass has more dispersive power than crown glass,because the spectrum which it produces is longer than that of crown glass. The dis-persion of a medium is indicated by the difference of refraction between the index ofrefraction of the red and the violet. Let us now see what efiect the dispersion has onimages produced by single lenses. White light a and b is falling on a double-convex lens (Fig. 29). The ray a is decom-posed into the different colored rays as soon as it enters the lens, and the red ray, as theleast refracted, will cross the axis p q in r, while the violet ray crosses the axis in v. Fig. 29. Fig. Between the red and violet the other colored rays cross the axis. The same is with theray b, and if we do not consider the s])herical aberration of the rays between a and b, all
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Keywords: ., bookcentury1800, bookdecade1880, bookidwilsonsquart, bookyear1887
