scholarly journals Interferometric measurements in the spectrum of the iron arc in air in the region λ 3100 — λ 3500

1931 ◽  
Vol 133 (822) ◽  
pp. 553-564 ◽  
Keyword(s):  
Wave Length ◽  
Systematic Difference ◽  
Vacuum Arc ◽  
International Astronomical Union ◽  
International Astronomical ◽  
Visible Part ◽  
Length Measurements ◽  
The Mean ◽  
Good Agreement ◽  
Made In

In a previous paper I gave the results of a set of wave-length measurements in the spectrum of the iron arc in the region λ 2300 to λ 3100. These measurements were carried out because it was found that previous measurements in this region were all rather unsatisfactory and gave results considerably higher than those calculated from levels determined from the wave-lengths recommended by the International Astronomical Union in 1928. My results confirm the values calculated from the I. A. U. Standards very satisfactorily, and also agree very well with the recent measurements of the vacuum arc by Burns and Walters. The apparatus was also used to measure a few lines in the visible part of the iron spectrum, and was shown to give results in excellent agreement with the values adopted by the I. A. U. in 1928. It was recommended by the I. A. U. that observations should be made in the region below λ 3400 for which there were no good modem measurements available. Accordingly the present work was undertaken to fill up the gap remaining and a set of 46 lines has been measured in the region λ 3100-λ 3500. The results are in very good agreement both with the I. A. U. calculated values and with the observed standards adopted by the I. A. U. in 1928, the mean systematic difference (J — I. A.) being only —0·0001 A. for 8 lines, while the mean accidental difference is ±0·0006 A. The agreement with the measurements of Babcock in the region λ 3370-λ 3500 is equally good, the mean systematic difference (J — B) being +0·0001 A. for eight lines, while the mean accidental difference is +0·0006 A.

scholarly journals Wave-lengths of the red lines of neon and their use as secondary standards

1933 ◽  
Vol 143 (848) ◽  
pp. 124-135 ◽  
Keyword(s):  
Wave Length ◽  
Great Intensity ◽  
International Astronomical Union ◽  
Interference Fringes ◽  
International Astronomical ◽  
Good Agreement ◽  
Strong Group

The spectrum of neon is dominated by a strong group of lines in the red. These are easily produced in an ordinary Geissler tube with very great intensity, and are sufficiently sharp to give measurable interference fringes with long path differences, of 120,000 waves or so. For these reasons the red lines of neon appear to be eminently suitable for use as secondary standards, and in view of the good agreement of the wave-length determinations of a number of observers (especially Burns, Meggers, and Merrill at the Bureau of Standards) they were adopted as secondary standards by the International Astronomical Union in 1922.

scholarly journals The red line of cadmium as a standard of wave-length

1936 ◽  
Vol 155 (885) ◽  
pp. 407-419 ◽  
Keyword(s):  
Wave Length ◽  
Point Of View ◽  
International Astronomical Union ◽  
Length Standard ◽  
Interference Fringes ◽  
High Tension ◽  
International Astronomical ◽  
Definition Of ◽  
Good Agreement ◽  
Red Line

The line 6438 of the first spectrum of cadmium was chosen by Michelson as the standard against which to measure the metre, because it was the best line he had discovered both from the point of view of its simplicity of structure and its capability of giving measurable interference fringes over very long paths. It has been used for comparison with the metre in four subsequent investigations and the wave-length 6438·4696 was adopted by the international Astronomical Union as the primary wave-length standard (or indeed the definition of the International Angstrom) in 1907. The line was produced by Michelson by exciting an H-shaped discharge tube with high tension alternating current, the lamp at the same time being raised to a temperature of 320° C with the aid of a furnace. Similar sources were used in six subsequent comparisons of the metre and the red line of cadmium. The results of these comparisons are in very good agreement, the accuracy appearing to be of the order of one part in five million, as can be seen from Table I.

scholarly journals Interferometric measurements in the arc spectrum of iron

1931 ◽  
Vol 130 (813) ◽  
pp. 395-410 ◽  
Keyword(s):  
Ultra Violet ◽  
Systematic Difference ◽  
Present System ◽  
International Astronomical Union ◽  
Pressure Shift ◽  
International Astronomical ◽  
The Mean ◽  
The Difference ◽  
Interferometer Method

At the 1928 Meeting of the International Astronomical Union at Leiden, it was recommended that the present system of iron secondary standards be extended further into the ultra-violet, since there are no modern measurements extending below about λ 3300. a list of wave-lengths computed from the standards adopted in 1928 in the less refrangible parts of the spectrum was given, which indicated that all the older measurements in this part of the spectrum were considerably in error, being over one part in one million too great. Accordingly I decided to measure a set of lines in the region λ 2300 to λ 3100 by means of the usual interferometer method. It was found that the measures agreed very well with the computed I. A. C. wave-lengths, the systematic difference being practically nil, while the mean accidental difference was less than 0.001 A. The wave-lengths also agreed very well with those determined recently by Burns in the vacuum iron arc spectrum; indeed, almost as well as they did with the I. A. C. computed values, although my values showed a very small (J - B = +0.0002 A.) systematic difference from Burns. The difference can be attributed to a pressure shift since it is about the amount to be expected for stable lines in this region, but it is too small to have any very great Significance. The agreement with Burn's 1930 revision of his 1913 interpolated measures was also fairly satisfactory, particularly from the absence of systematic difference, although the accidental differences were rather greater. There is however, considerable disagreement with all the old interpolated measurements which are based on Buisson and Fabry's standards and also with Buisson and Fabry's measurements.

scholarly journals 14. Commission des Étalons de Longueur D’Onde et des Tables de Spectres Solaires

1939 ◽  
Vol 6 ◽  
pp. 79-102
Author(s):  
M. W. F. Meggers ◽  
MM. Babcock ◽  
Buisson ◽  
Burns ◽  
Ch. Fabry ◽  
...  
Keyword(s):  
Wave Length ◽  
Primary Standard ◽  
International Committee ◽  
International Astronomical Union ◽  
International Union ◽  
Weights And Measures ◽  
International Astronomical ◽  
Solar Research ◽  
Definition Of ◽  
Red Radiation

The red radiation, 6438.4696 A., emitted by a cadmium lamp of Michelson type was first chosen in 1907 by the International Union for Co-operation in Solar Research (Trans. I.U.S.R. 2, 109, 1907) as a definition of the unit of wave-length. This primary standard was subsequently adopted by the International Astronomical Union (Trans. I.A.U. 1, 35, 1922) and by the International Committee on Weights and Measures (Procès-Verbaux Comité Int. Poids et Mesures (2), 12,67,1927). Specifications for the production of this primary standard were adopted provisionally by the I.A.U. in 1925 (Trans. I.A.U. 2, 47, 232, 1925), and by the I.C.W.M. in 1927 (Procès-Verbaux Comité Int. Poids et Mesures (2), 12, 67, 1927). Three reports of this Commission (Trans. I.A.U. 3, 77, 236, 1928; ibid. 4, 58, 233,1932; ibid. 5, 81, 299, 1935) have discussed the divergences in these specifications and pointed out the unsatisfactory features of each. This discussion culminated in a revised specification (Trans. I.A.U. 5, 303, 1935) which was adopted unanimously by the I.C.W.M. in 1935 (Procès-Verbaux Comité Int. (2), 17, 91,1935).

scholarly journals The molecular scattering of light in vapours and in liquids and its relation to the opalescence observed in the critical state

1922 ◽  
Vol 102 (715) ◽  
pp. 151-161 ◽  
Keyword(s):  
Critical Point ◽  
Critical State ◽  
Incident Light ◽  
Wave Length ◽  
Molecular Scattering ◽  
Avogadro’S Number ◽  
Quantitative Manner ◽  
The Mean ◽  
Good Agreement ◽  
Molecular Scattering Of Light

It has long been known that in the immediate vicinity of the critical state, many substances exhibit a strong and characteristic opalescence. In recent years, the phenomenon has been studied by Travers and Usher in the case of carefully purified CS 2 , SO 2 , and ether, by S. Young, by F. B. Young in the case of ether, and in a quantitative manner by Kammerlingh Onnes and Keesom in the case of ethylene. An explanation of the phenomenon on thermodynamic principles as due to the accidental deviations of density arising in the substance was put forward by Smoluchowski. He obtained an expression for the mean fluctuation of density in terms of the compressibility of the substance, and later, Einstein applied Maxwell’s equations of the electromagnetic field to obtain an expression for the intensity of the light scattered in consequence of such deviations of density. He showed that the fraction α of the incident energy scattered in the substance per unit volume is 8 π 3 /27 RT β ( μ 2 – 1) 2 ( μ 2 + 2) 2 /N λ 4 (1) In this, R and N are the gas constant and Avogadro’s number per grammolecule, β is the isothermal compressibility of the substance, μ is the refractive index and λ is the wave-length of the incident light. Keesom tested this formula over a range of 2·35° above the critical point of ethylene and found good agreement except very close to the critical point.

The dispersion of matter in turbulent flow through a pipe

1954 ◽  
Vol 223 (1155) ◽  
pp. 446-468 ◽  
Keyword(s):  
Turbulent Flow ◽  
Capillary Tube ◽  
Resistance Coefficient ◽  
Mean Flow ◽  
Combined Action ◽  
Flow Through ◽  
The Mean ◽  
Coefficient Of Diffusion ◽  
Good Agreement ◽  
Made In

The dispersion of soluble matter introduced into a slow stream of solvent in a capillary tube can be described by means of a virtual coefficient of diffusion (Taylor 1953 a ) which represents the combined action of variation of velocity over the cross-section of the tube and molecluar diffusion in a radial direction. The analogous problem of dispersion in turbulent flow can be solved in the same way. In that case the virtual coefficient of diffusion K is found to be 10∙1 av * or K = 7∙14 aU √ γ . Here a is the radius of the pipe, U is the mean flow velocity, γ is the resistance coefficient and v * ‘friction velocity’. Experiments are described in which brine was injected into a straight 3/8 in. pipe and the conductivity recorded at a point downstream. The theoretical prediction was verified with both smooth and very rough pipes. A small amount of curvature was found to increase the dispersion greatly. When a fluid is forced into a pipe already full of another fluid with which it can mix, the interface spreads through a length S as it passes down the pipe. When the interface has moved through a distance X , theory leads to the formula S 2 = 437 aX ( v * / U ). Good agreement is found when this prediction is compared with experiments made in long pipe lines in America.

Argon vacuum wave-length measurements

1953 ◽  
Vol 218 (1135) ◽  
pp. 577-586 ◽  
Keyword(s):  
Standard Error ◽  
Wave Length ◽  
Systematic Difference ◽  
Length Measurements ◽  
Significant Figures

The vacuum wave-lengths of 84 lines of the argon spectrum in the region 3500 to 4500 Å have been measured using two reflecting echelons. Since the standard error of the most favourable lines is only ± 0·0001 Å and less than ± 0·0002 Å for 53 of the lines, there is some justification in expressing the wave-lengths to eight significant figures. As no systematic difference between wave-lengths determined with each echelon has been found, the method is independent of the particular instrument employed. A discussion of the non-linearity of dispersion is given, and it is shown that it may be assumed linear for the particular echelons used without introducing appreciable error.

scholarly journals On the spectra of isotopes

1920 ◽  
Vol 96 (679) ◽  
pp. 388-395 ◽  
Keyword(s):  
Experimental Error ◽  
Previous Investigation ◽  
Wave Length ◽  
Sixth Order ◽  
Mean Error ◽  
Interference Fringes ◽  
The Mean ◽  
Concave Grating ◽  
Made In

In a previous investigation a comparison was made of a number of lines in the spectra of ordinary lead and of lead of radio-active origin. The wave­-lengths of seven lines in each case were measured from plates taken with a concave grating, and were found to be identical for the two varieties of lead within the limits of experimental error, which was about 0·03 A. A further examination was made in the case of the line λ = 4058 A., which is the brightest line in the spectrum, by measurement of the interference fringes obtained by means of a Fabry and Perot étalon , and it was concluded that any difference between the wave-lengths of this line in the two varieties of lead was less than 0·003 A., which was the mean error in these measurements. Aronberg has recently made a comparison of the wave-length of the line λ = 4058 A. in the spectrum of ordinary lead, and of lead obtained from Australian carnotite, and from measurements made on plates taken in the sixth order of a 10-inch Michelson grating, has found that the wave-length of this line in the spectrum of the lead of radio-active origin is less re­frangible than the line in the spectrum of ordinary lead by 0·0043 A.

Further Observations on the Plants Eaten by Kangaroos and Sheep Grazing Together in a Paddock in South-Western Queensland

1974 ◽  
Vol 1 (1) ◽  
pp. 27 ◽  
Author(s):  
M Griffiths ◽  
R Barker ◽  
L Maclean
Keyword(s):  
Species Difference ◽  
Severe Drought ◽  
N Content ◽  
Plant Parts ◽  
Red Kangaroo ◽  
Grey Kangaroo ◽  
Faecal Samples ◽  
The Mean ◽  
Good Agreement ◽  
Made In

In 8 periods between February 1967 and June 1968, covering a severe drought and subsequent rain, samples of 66 species of dicotyledons and 50 species of monocotyledons were collected from a large paddock in semiarid 'mulga-box' country in south-western Queensland. The mean N content of the dicotyledons ranged from 1.51 to 2.85 g/100 g DM, and that of the monocotyledons from 0.70 to 1.86 g/100 g DM.Stomach or faecal samples were analysed for plant parts. When known plant mixtures were given to 2 grey kangaroos (Macropus giganteus) and two sheep there was no species difference in the digestibility of the different plants or in the size distribution of faecal particles. Comparison of stomach and rectal samples from 5 shot kangaroos and 7 shot sheep showed quite good agreement. Samples of the faeces of sheep, grey kangaroo and a few red kangaroo (Megaleia rufa) were collected from the ground at the same intervals as the plant samples, dried and analysed for N and for plant parts. Detailed results are given. The grey kangaroos consistently ate more grasses than the sheep. The N content of sheep faeces was higher than that of kangaroo faeces, reflecting the higher protein intake of the sheep. The results confirm those of an earlier study (NAR 38, 1829) made in 1963–4 in a period of average rainfall. The authors conclude that competition between sheep and kangaroos is small.

The Characteristics of Spiral Vortex Flow at High Taylor Numbers

1979 ◽  
Vol 21 (2) ◽  
pp. 65-71 ◽  
Author(s):  
M. M. Sorour ◽  
J. E. R. Coney
Keyword(s):  
Vortex Flow ◽  
Hydrodynamic Instability ◽  
Wave Length ◽  
Axial Direction ◽  
Outer Wall ◽  
Mean Flow ◽  
Annular Gap ◽  
Spiral Vortex ◽  
The Mean ◽  
Made In

This experimental investigation is devoted to the study of combined axial and rotational flow in a concentric annular gap, of radius ratio 0.8, formed by a stationary outer and a rotatable inner cylinder. Taylor numbers varying from the critical to an order of 106 will be considered. The investigation is divided into three parts, illustrating different aspects of spiral vortex flow. Firstly, the evolution of the flow with increasing Taylor number at a constant axial Reynolds number is studied by the analysis of the spectrum of the signal from a hot-wire anemometer. Secondly, the wave length and drift velocity of the spiral vortices are determined for the axial direction. Thirdly, the effects of hydrodynamic instability on the mean flow are investigated. It should be noted that the first and second parts are under adiabatic conditions, while the third is both adiabatic and diabatic, heat being transferred isothermally through the outer wall of the annular gap. Also, all of the measurements were made in the fully-developed region of the flow.

Sign in / Sign up

Export Citation Format

Share Document