Interferometer Experiments in Acoustics and Gravitation ...

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Carnegie institution of Washington, 1921 - Gravitation
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Page 74 - BY CARL BARUS DEPARTMENT OF PHYSICS, BROWN UNIVERSITY Communicated July 1, 1920 1. Apparatus. — These experiments were undertaken to find in how far interferometer methods might contribute to the measurement of changes of g, under conditions in which the pendulum is inapplicable. The apparatus as a whole is a horizontal torsion balance with the deflection readable in terms of the displacement of the achromatic interference fringes. The method developed would be applicable in case of any ordinary...
Page 2 - When the pressure increments exceed a certain small value, the plates gg' no longer rise and fall in parallel. The coincidence of images is destroyed and the fringes vanish. There is here a conflict with the capillary forces present at the edges of the disc. I endeavored to improve this by using small plates gg', anchored near the centre of MM
Page 9 - To determine the specific inductive capacity of a given insulating plate, the electrophorus is discharged at a convenient distance, d', between plate and hard rubber face. The insulator (Kg) is then inserted (noting the fringe displacement n) and withdrawn. The fringes must return to zero, showing that no charge has been imparted by the friction of the insulator. The upper plate is now depressed (y) on the micrometer screw until the same fringe displacement n is obtained. The operation is quite rapid;...
Page 4 - ... heating produced was 2 X 10~4 C. per second. Whether, supposing A A' to be filled with water, a pyrheliometer may be constructed on this principle I have yet to learn. Other interesting results of the same kind might be mentioned. Thus if the screw stopcock, figure 2, is closed quickly (C being open) there is always a decided increment of pressure. In other words in consequence of the viscosity of air, the fine space at the plug is virtually a closure before the screw is checked by an actual...
Page 3 - In the experiments fringes of 1/2 scale part were installed. In separate experiments immediately after closing the cock C, a half turn of the screw produced a displacement of 8.3, 8.0, 8.0, 8.5, 8.5 scale parts, as the average, therefore 16.4 scale parts per turn or about 33 fringes per turn. This agrees as closely as may be expected with the number computed. The pressure increment per turn of screw is dp = n/2 cm. of mercury or per turn of screw about 10"
Page 1 - BB' should be mounted separately from the interferometer. If it is placed on the base of the latter, all manipulations there shake the mercury in BB' and it is necessary to wait for subsidence. This, however, occurs very soon, so that the separate mounting is not absolutely necessary. Without manual interference the fringes are about as quiet as in a solid apparatus. 2. Experiments. — To test this apparatus the air space A A' was left with a plenum of air. With A...
Page 100 - They were then put away in a dark vault of nearly constant temperature, for short time ranges, to be examined from time to time as to the displacement of the thread of water within: for it will be seen that the meniscus under a' is at a pressure excess of hpg as compared with the meniscus under a.
Page 23 - R'. A variety of correlative experiments were made with the simple (nondifferential) apparatus (tb R closed R' D a open). I have elsewhere referred to the absence of fringe displacement (nearly) when the copper foil carrying the pinhole is cemented to the mouth of a funnel tube; but the prolongation of the quill tube t", if the diameter is not increased, is almost indefinitely permissible. The experiments made suggest a method of obtaining an effect which is at least apparently differential. For...
Page 97 - FIGS. 1 AND 2 found with the extremely simple apparatus, figure 1 . The swimmer being here lighter than water, AA is the standglass, wholly filled and a, b, the swimmer held down at a definite level by the thermometer T. M is a water manometer for registering the pressure excess at which flotation just occurs at the given level. Pressure is applied by aid of the small water reservoir, R, communicating with AA by the tube t with the stopcock F, and the flexible pipe p , the whole system t F p R being...
Page 13 - ... .1 mm. micrometer. It is perhaps advantageous to place the micrometer in the wide slit of the collimator, the fringes being parallel to the scale parts. To obviate the need of adjusting the inclination of the fringes (as this frequently changes), the slit holder should be revolvable around the axis of the collimator, the scale being parallel to the length of the slit and the fringes moving in the same direction across the white ribbonlike field. Fringes equal to a scale part in breadth are most...

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