Optical Tables and Data for the Use of Opticians

Optical Tables and Data for the Use of Opticians

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 edition. Excerpt: ...those prescribed could be substituted, to produce the same optical elfect. In a great many cases such transpositions are possible, and to explain thee we will deal briefly with the underlying principles. The subject has already been touched upon from one point of view when treating with crossed cylinders. I. Transposition of Simple O'ylindcrs.--It is clear from the con-sideration of simple spherical lenses, that two cylindrical lenses of equal and opposite powers, when placed together upon the same optic axes with their axes of figure parallel have, as a whole, no efiect as a lens. Suppose then, in front of any given cylinder, We place such a. pair of individual power numerically equal to that of the given cylinder, and with their axes per-pendicular to its axis. Then the combined effect of the three is the same as that of the given cylinder alone; but we may regard them as two crossed cylinders of equal power, and a third of equal but opposite power with its axis perpendicular to flat of the given cylinder. Now two crossed cylinders of equal and like power may be replaced by a sphere of equal and like power. We are then left with a sphere of power equal to that of the given cylinder, and a cylinder of equal but opposite power on an axis at right angles. Thus we arrive at the first guiding principle: -Any given cylinder may be replaced-by a sphere of the same power, and a cylinder of equal but opposite power on an axis at right angles. _ Now what has been said regarding powers is equally true of curvatures for the power of any refracting surface is its cur-vature multiplied by the constant (p.--1) Hence the rule may be paraphrased as---Any given cylinder may be replaced by a sphere of equal numerical curvature, and a cylinder of equal but...show more

Product details

  • Paperback | 26 pages
  • 189 x 246 x 1mm | 68g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236818881
  • 9781236818881