The Electrical Review Volume 10

The Electrical Review Volume 10

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1882 edition. Excerpt: ... usual form of Bunsen's photometer is shown in fig. 4, in which a b is an optical bank, divided into feet and inches, or into centimetres. At one end is placed upon a suitable support the burner, L, which is to be compared with the normal candle, /, at or near the other end. The paper screen, s, with a central spot waxed or stearined, is attached to a slide, which is movable between the two lights, the balance being reached when the screen is equally illuminated from both sides, and the wax-spot disappears. Then the illuminating powers of the lights are proportional to the squares of their respective distances, D and d, from the screen. The total disappearance of the wax-spot in Bunsen's photometer is, however, a point which is seldom or never satisfactorily reached; and, moreover, it is generally found that when a balance is obtained the slightest shifting of the eye of the observer is sufficient to bring the wax-spot back again into view. A very common modification of Bunsen's photometer is the so-called mirror photometer. It consists of a white paper screen with its wax-spot, mounted between two plane mirrors, so that the operator sees at the same time the reflections of both sides of the screen. The screen is placed in a small wooden frame, A n (fig. 5); M N and M' N' are the two mirrors, forming an obtuse angle, divided into equal parts (in plan) by the frame, A n. The operator placed in front sees the reflections of both faces of the screen. The two lights to be compared are situated one at the right hand, the other at the left, so that each face of the paper can only be illuminated by one of the lights, the distances of which are adjusted until the reflections of the central wax-spot disappear. Wheatstone's Photometer, fig. C, consists more

Product details

  • Paperback | 718 pages
  • 189 x 246 x 37mm | 1,261g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236547810
  • 9781236547811