The Interferometry of Reversed and Non-reversed Spectra, Parts 3-4

Carl Barus

Carnegie Institution of Washington, 1919 - Interference (Light)

Contents

• The Displacement Interferometry of Long Distances 1 Introduction: 7
• Apparatus Fig 1: 8
• Ocular micrometer Fig 4 II: 16
• Direct observations: 18
• Indirect observations Fig 6: 21
• Compensators Figs 7 8: 25
• Types of achromatic fringes: 27
• The Interferometry of Small Angles Methods by Direct and Reversed Superposed Spectra 14 Introductory: 29
• Estimate: 30
• Equations: 31
• Observations Prismprism method Fig 16: 34
• Interference from rough surfaces Figs 17 18: 36
• Reversed rays Figs 19 20 21: 37
• Second method Figs 22 23: 40
• Equations: 41
• Observations Figs 24 25: 46
• Fringes from rough surfaces: 48
• Direct interferences without cleavage prism Fig 26: 49
• The Elastics of Small Bodies: 53
• Introductory method Fig 27: 56
• The same Thinner rods hard rubber Figs 40 41 42 43: 61
• The same Glass Fig 44: 63
• The same Steel: 64
• Apparent yield within the apparatus: 66
• Ocular micrometer Collimator micrometer: 68
• Summary Figs 50 51: 73
• Observations Floating system Figs 52 53: 74
• Expeditious fringe detection: 75
• Heavy needle in air: 76
• Summer experiments: 79
• Introductory: 83
• Observations Fig 61: 91
• Apparatus Figs 1 2 3: 1
• Equations Fig 4: 4
• Apparatus Figs 7 8: 7
• Observations Hard rubber Figs 9 10 Table 1: 12
• Introductory: 13
• Apparatus Fig 29: 29
• Observations Figs 30 31: 30
• Further observations Figs 33 34 Table 3: 33
• Coefficient of expansion Figs 37 38 39: 37
• Equations Fig 40: 38
• Available liquids: 39
• An Electrodynamometer Using the Vibration Telescope 26 Introductory 27 Apparatus Figs 41 42 43: 41
• Observations Figs 44 45: 44
• Further observations Fig 46 Table 4: 47
• Adjustable telephone 33 Coil tester Figs 52 53 54: 48
• Heavier armature and less damping Fig 55: 51
• Further magnification Fig 56 Table 5: 53
• Equations: 54
• Introductory: 55
• 13: 61
• Direct telephonic induction Figs 70 71 72 73 74: 64
• Telephonic apparatus Figs 66 67 91: 66
• Further observations Figs 72 73 96: 72
• 16: 73
• Index of refraction irrespective of form: 78
• Micrometer measurements Table 7: 85
• 24: 86
• Equations Two reflections: 92
• Monochromator Figs 100: 98
• Miscellaneous Results of the Preceding Experiments: 104
• The triangular selfadjusting interferometer Fig: 110
• 29: 114
• Introductory: 116
• 30: 117
• w w w w cu 37 37 38 38 39 廿七 44 45 46 47 48 48 51 52 53 54 CHAPTER VI The Rapid Telephonic Vibrator on the Interferometer 40 Observatio...: 118

Popular passages

Page 70 - If a direct-vision prism or grating is placed in front of the telescope, the spectrum is seen to be crossed by intense black lines, very nearly parallel and horizontal, but actually diverging from blue to red symmetrically up and down from the horizontal central black line. It is not necessary here, that the slit be fine. In fact, it may be several millimeters broad without destroying these spectrum fringes, if essentially horizontal.‎

Page 24 - Xio-6 cm. It is interesting, therefore, to note that the current must exceed 0.02 ampere before any elongation can be detected. After this, however, the elongations abruptly begin and increase rapidly to a maximum, which is reached before saturation. They then decrease somewhat more slowly and eventually become negative. In the strong fields the contact lever is thrown into violent vibration on closing the circuit, and the reading is less certain. The next experiments, figure 31, were made with somewhat...‎

Page 34 - This may be done by selecting relatively thick- walled tubes of small external diameter. A few data are here desirable. Using an ocular micrometer plate i cm. long with scale-parts of 0.oi cm. each and fringes of moderate size (i or 2 scale-parts in width) we may write as in the preceding paper, (7) A/// = 3Xio-'A<?‎

Page 91 - A change of the tension of the wires ee' in figures 70 and 71, or any adjustments at the telephones, calls for a fresh search for fringes; but this is not difficult if the spectro-telescope is first used and the admonitions relative to the objective coincidence of pencils entering the telescope, as well as their parallelism, as above explained, are given consideration. These difficulties do not enter when the mirrors can be displaced normally to the incident rays. In addition to the telephone tt'...‎

Page 10 - These stresses act in the direction ar and fd collinearly, and there are no couples endangering the accuracy of the elastic displacements of r. The stress is standardized in terms of the observed rotation of the thumb-nut w . Figure 7 (a) to (d) are details, showing different methods of clutching the rod r. Figure 8 shows a similar apparatus in the same notation. Here the spring SS acts by tension and more and more strongly as the thumb-nut u; advances/.‎

Page 62 - The stretched ellipses, which follow immediately after the change of aspect of the telephone bobbin to the magnetic lines, are noteworthy. They indicate the inductive effect of the reversal of the magnetic field, impressed on the vibrating system and observed in spite of it. Ellipses cross over, or change sign of rotation, at 2 and 6', but not near 3' or 5, the latter being oscillations.‎

Page 8 - The fluctuation of data is due to air-currents across the interferometer. It was not easy to obviate these, and it was not thought necessary for the present purposes. Otherwise the data would have been smooth. There is no doubt that a linear relation may be assumed. In curve a the readings of the interferometer micrometer increase, in curve b they decrease. If the means be taken from doublets far apart the ratios are (a) AN /Ae = 0.003i0 (b) AN/Ae = 0.003 io and they happen to coincide.‎

Page 91 - The fibers e,e' were about 45 cm. long and their distance apart about 29 cm. Their period and that of the vibrating telescope were made about the same, on the average about 0.2 sec., and this was for convenience nearly the same as the period of the vibrating telescope and of the induced alternating current. It is convenient to insert an extra telephone (resistance about...‎

Page 37 - P is e' and the angle of incidence i', the path-difference will be 2e' cos i'. As in the preceding experiment, the mirror at n may be a half -silver, so that the ray d' passes through it and may then be returned in its own path by a mirror at n‎

Page 88 - If x is the fraction of light reflected, that entering the telescope should be proportional to x( i —x)*, which is a maximum when x = %. The experiments, however, show no serious difficulty from deficient light, 67. Equations. Two reflections. — The equations for this case are somewhat more involved than the preceding; but it suffices to accept for the angle of incidence i at the cylinder G, figure 89, the value given by the old-fashioned theory of the rainbow, viz...‎

Bibliographic information

• Title: The Interferometry of Reversed and Non-reversed Spectra, Parts 3-4; Volume 249 of Carnegie Institution of Washington publication; The Interferometry of Reversed and Non-reversed Spectra, Carl Barus
• Author: Carl Barus
• Publisher: Carnegie Institution of Washington, 1919
• Original from: Harvard University
• Digitized: Sep 7, 2007