Carnegie Institution of Washington Publication Volume 149

Carnegie Institution of Washington Publication Volume 149

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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. 1911 edition. Excerpt: ...object. In fact, the grating as in equation (1) is alternately reinforced by a column of dense and rare air through which the beam travels at normal incidence. If AN be the difference of the micrometer readings for the two positions, equa tion (2), in which the dispersion of air is neglected, is to be modified in the way suggested for equation ( 1), so that for the D line of the spectrum as fiducial Here e is the length, )J0 and p the respective indices of refraction for the high and low densities of the column of air. Equation (2') is, however, apparently too cumbersome for use at the outset, so that equation (2) has been preferably admitted for experimental purposes, the dispersion of air being disregarded. The values of AN so found are too large and the consequent values of 7 all too small. They will be corrected, however, in 97, in which the theory is to be developed in full. It will then be found that the data of the interference method agree with the data of the mechanical method as nearly as may be expected. In fig. 59 the pencil of light c enters from a collimator at C and encounters the grating G at a small angle of incidence I. The reflected undeviated beam n is returned by the stationary opaque mirror N, the transmitted beam m by the movable opaque mirror M on the micrometer, after which both enter the telescope R. The arms m and n of the interferometer are of gas-pipe and provided with a circulation of cold water at constant temperature, though in the present chapter this is not needed. The micrometer at M is graduated to 0.0005 cm. on the drum and easily read off by estimation or vernier to 0.00005, 1'.e., to the mean wave-length of light. The tests below show that the center of ellipses may be placed on a more

Product details

  • Paperback | 88 pages
  • 189 x 246 x 5mm | 172g
  • United States
  • English
  • black & white illustrations
  • 1236827686
  • 9781236827685