scholarly journals The absorption of hard monochromatic γ-radiation

1930 ◽  
Vol 128 (807) ◽  
pp. 345-359 ◽  
Keyword(s):  
Absorption Coefficient ◽  
High Frequency ◽  
Wave Length ◽  
Low Frequency ◽  
Photoelectric Effect ◽  
Fourth Power ◽  
X Rays ◽  
Photoelectric Absorption ◽  
Initial Direction ◽  
Γ Radiation

Energy may be removed from a beam of γ -rays traversing matter by two distinct mechanisms. A quantum of radiation may be scattered by an electron out of its initial direction with change of wave-length, or it may be absorbed completely by an atom and produce a photoelectron. The total absorption coefficient, μ, is defined by the equation d I/ dx = -μI, and is the sum of the coefficients σ and τ referring respectively to the scattering and to the photoelectric effect. For radiation of low frequency, such as X-rays, the photoelectric absorption is very much more important than the absorption due to scattering, and many experiments have shown that the photoelectric absorption per atom varies as the fourth power of the atomic number and approximately as the cube of the wave-length. For radiation of high frequency, such as the more penetrating γ -rays, the photoelectric effect is, even for the heavy elements, smaller than the scattering absorption; and, since the scattering from each electron is always assumed to be independent of the atom from which it is derived, it is most convenient to divide μ. defined above by the number of electrons per unit volume in the material and to obtain μ e the absorption coefficient per electron.

scholarly journals The absorption of X-rays

1918 ◽  
Vol 94 (664) ◽  
pp. 510-524 ◽  
Keyword(s):  
Absorption Coefficient ◽  
Atomic Absorption ◽  
Atomic Number ◽  
Wave Length ◽  
Fourth Power ◽  
X Rays ◽  
Absorption Coefficients ◽  
Characteristic Radiation ◽  
Crystal Face ◽  
X Ray

Introduction . —Previous to the discovery of the behaviour of X-rays with regard to crystals, the most homogeneous radiation obtainable was that of the characteristic radiation of an element which is excited when that element is exposed to X-radiation of suitable hardness. These characteristic radiations are now found, however, by the new method of analysis, to be constituted of a number of radiations of different wave-lengths. Moseley, shortly after the discovery of the reflection of X-rays, showed that the characteristic radiations of most of the metals he examined consisted of two prominent wave-lengths; Bragg later found that, in the case of rhodium, palladium and silver, each of these lines could be further resolved into two components. Hence the spectra of the characteristic radiation of the K series of these elements consist of at least four different wave-lengths. The analysis of a beam of X-rays into its constituent radiations by reflection at a crystal face provides a means, therefore, of obtaining radiation of a definite wave length and of such intensity as to enable its absorption coefficient in different materials to be accurately measured. Bragg and Pierce have already measured the absorption coefficients of the two most prominent lines in the spectra of the elements Rh, Pd and Ag, in a number of metals. To make the absorption coefficient more directly comparable with other atomic characteristics, they gave their results in the form of atomic absorption coefficients: the atomic absorption coefficient expresses the proportion of the energy of an X-ray pencil which is absorbed in crossing a surface on which lies one atom to every square centimetre. The ordinary mass absorption coefficient can be calculated from this quantity by dividing it by the mass of the absorbing atom. The experimental results showed that the ratio of two absorption coefficients is independent of the wave-length of the radiation over considerable ranges, a result previously deduced by Barkla from his experiments; also, that the atomic absorption coefficient is proportional to the fourth power of the atomic number of the absorber.

The Photoelectric Absorption of Gamma Rays

1931 ◽  
Vol 27 (1) ◽  
pp. 103-112 ◽  
Author(s):  
L. H. Gray
Keyword(s):  
Absorption Coefficient ◽  
Atomic Number ◽  
Gamma Rays ◽  
Wave Length ◽  
X Rays ◽  
Photoelectric Absorption ◽  
Empirical Law ◽  
Γ Rays ◽  
Image Position

No satisfactory formula has so far been derived theoretically for the photoelectric absorption of X-rays and γ-rays. The empirical lawhas hitherto been generally accepted as giving approximately the variation of the photoelectric absorption coefficient per electron, with atomic numberZand wave length λ for X-rays of wave length greater than 100 X.U., and the validity of this law has often been assumed for γ-rays also.

The relative absorbing powers of the L-levels for radiation of varying wave-length

1924 ◽  
Vol 22 (3) ◽  
pp. 379-392 ◽  
Author(s):  
H. W. B. Skinner
Keyword(s):  
Absorption Coefficient ◽  
Wave Length ◽  
The Other ◽  
X Rays ◽  
A Value ◽  
The Law ◽  
Absorption Wave

1. Changes in the relative intensities of the lines in the fluorescentL-spectrum of Cerium excited by radiation of various wave-lengths have been observed.2. These results imply a change in the relative absorbing powers of the threeL-levels as the wave-length of the absorbed radiation diminishes from a value just below the absorption wave-length of theL-levels to a value considerably below. The absorbing power of theLI-level becomes increased relative to the absorbing powers of the otherL-levels as the wave-length diminishes. The results agree with those published by H. Robinson in a recent paper.3. These results imply a breakdown of the law that μ/λ3is a constant (where μ is the absorption coefficient of X-rays of wave-length λ) as applied to theindividual L-levels of an element.4. A comparison is made between the above results, and some results on the relative absorbing process of theL-levels obtained by Ellis and Skinner from β-ray spectra.

Development of Sound Absorbers for Large Spaces

2005 ◽  
Vol 12 (4) ◽  
pp. 237-254
Author(s):  
Yoshihito Kobayashi ◽  
Toshiya Kitamura ◽  
Shinji Yamada
Keyword(s):  
Absorption Coefficient ◽  
Resonance Frequency ◽  
High Frequency ◽  
Sound Absorption ◽  
Low Frequency ◽  
Frequency Bands ◽  
Sound Fields ◽  
Absorption Area ◽  
Translucent Material ◽  
The Chairs

Moulded chairs have been developed, in which sound absorption at low frequency bands is increased by using the seat section and/or the back section as a resonator. In addition, a translucent sound absorption panel has been developed for application in large spaces. In the case of the chairs the resonance frequency, determined by the position, number, and depth of the holes, was examined. Prototypes were constructed, and the equivalent absorption area was measured in a reverberation room. The resonators of the chairs achieved an equivalent absorption area of 0.15 m2/seat, in the 125 Hz band. For the case of the translucent material, sound absorption was measured and compared with conventional sound absorption materials. The panels were designed in order to control sound fields in large spaces. The panels achieved a sound absorption coefficient of 0.6 to 1.0 at middle and high frequency bands.

scholarly journals Sifat Komposit Dari Bahan Serat Akar Wangi Dan Limbah Serbuk Gergajian Kayu Sebagai Bahan Aklternatif Peredam Suara

2017 ◽  
pp. 136
Author(s):  
Purwanto Purwanto
Keyword(s):  
Absorption Coefficient ◽  
High Frequency ◽  
Sound Absorption ◽  
Low Frequency ◽  
Weight Fraction ◽  
A Value ◽  
Test Instrument ◽  
Alternative Materials ◽  
Small Tube ◽  
Absorption Power

The increasing use of composites in all fields is engineered materials that many people do to obtain the new alternative materials, one of the materials such as natural vetiver fiber (SAW) which is strong and lightweight and powder sawn (SGK), which is waste material. In this research, manufacturing the composite of  SAW and SGK then testing acoustic/absorption power by measuring the absorption coefficient of the sound and the observation of microstructure. The method used in the study is an experiment in the laboratory to make composites based on the ratio of the weight fraction between SAW and SGK from 1: 5, 2: 5, 3: 5, 4: 5 and 5: 5. Having formed the composites, then the specimen has made by an acoustic test that compatible to ASTM E-1050-98 standard with B & K 4206 Small Tube Set test instrument. Furthermore, to determine the composition of fibers in the composites, there do the micro observation. From the results of the show the composites produced the sound absorption ability for the low frequency (1000 Hz) with an absorption coefficient (α) of 0.25 occurred in comparative fraction of 2: 5 (SAW20, SGK50). While at high frequency (5000 Hz) has a value of coefficient (α) of 0.41 occurred in the ratio of 1: 5 (SAW10, SGK50). The number of composition number fiber influence the composite tensile strength and micro observations occurred in the composition ratio of 5: 5 its highest strength.

scholarly journals A critical-absorption photometer for the study of the Compton effect

1928 ◽  
Vol 119 (783) ◽  
pp. 526-530
Keyword(s):  
Absorption Coefficient ◽  
Wave Length ◽  
Light Element ◽  
Compton Effect ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Length Changes ◽  
Absorption Measurements ◽  
Ray Scattering

That a change of wave-length occurs in X-ray scattering was first indicated by absorption measurements with the ionisation chamber, which showed that the absorption coefficient of a light element like aluminium was slightly greater for the scattered than for the primary X-rays. Later more conclusive and direct evidence was obtained when spectrometric analysis of the scattered X-rays was made first by the ionisation and afterwards by the photographic method. This analysis disclosed the existence of an unshifted as well as the shifted line, and showed also that the latter becomes relatively more prominent with diminishing wave-length and lower atomic number of the scattering element. After the main features of the Compton effect were established by means of spectrometric measurements, however, absorption measurements with the ionisation method have again been employed for a detailed study of the phenomenon, for such measurements are much quicker than the spectrum experiments, where the final energy available is much smaller on account of the double scattering involved. As mentioned above, the absorption measurements were based on the slight increase in the absorption coefficient of a light element when the wave-length changes from the unmodified to the modified value. The much larger and sudden diminution in absorption of X-rays when the frequency is altered from the short to the long wave-length side of the critical K-absorption limit of the element used as a filter, furnishes us with an easy and convenient method of exhibiting the wave-length change in X-ray scattering. In the present paper will be described a photographic wedge photometer based on this principle, which enables the characteristics of the Compton effect to be readily observed. It may be pointed out that the same idea could no doubt be utilised also in connection with the ionisation measurements of the Compton effect.

THE ULTRAVIOLET ABSORPTION OF SILVER BROMIDE

1953 ◽  
Vol 31 (2) ◽  
pp. 218-224 ◽  
Author(s):  
J. R. Allen
Keyword(s):  
Absorption Coefficient ◽  
High Dielectric Constant ◽  
Wave Length ◽  
Ultraviolet Absorption ◽  
Silver Bromide ◽  
Absorption Process ◽  
Photoelectric Absorption ◽  
Spectral Edge ◽  
High Dielectric ◽  
Positive Hole

The photoelectric absorption process in solid insulators is discussed and contrasted with that for free atoms and ions. It is suggested that in substances of high dielectric constant the resultant screening of the field of the remaining positive hole due to the polarization of the material results in a reduction of the absorption coefficient at the spectral edge, and produces a maximum at higher energies. This effect is illustrated by a calculation of the ultraviolet absorption coefficient of silver bromide using as a model a bromine ion in a hole in a uniform dielectric. The calculated absorption coefficient is found to rise from the edge to a maximum at a wave length of about 850 Å.

Analysis about the Effect on the Design of the Diffusers

2012 ◽  
Vol 174-177 ◽  
pp. 2016-2019
Author(s):  
Hui Yu Chen ◽  
Jing Gong
Keyword(s):  
Body Size ◽  
Absorption Coefficient ◽  
High Frequency ◽  
Large Body ◽  
Low Frequency ◽  
Groove Depth ◽  
The Body ◽  
Frequency Sound ◽  
High Absorption Coefficient ◽  
High Absorption

In order to study the effect of the diffusers,there has been designed a variety of diffusers.If groove depth is large , the diffuser will become a high absorption coefficient, low-frequency sounds will reduce significantly. So we have spread the body size nested within each other, a small has been nested in a large body .The smaller parts expand of high-frequency sound, the larger parts for low-frequency sound, so over a wide frequency band can been spreading.

scholarly journals On the intensity of total scattering of X-rays

1929 ◽  
Vol 124 (793) ◽  
pp. 119-142 ◽  
Keyword(s):  
High Frequency ◽  
Scattered Radiation ◽  
Wave Length ◽  
Incident Radiation ◽  
Compton Effect ◽  
X Rays ◽  
Free Electrons ◽  
Scattering Angle ◽  
Total Scattering ◽  
Monatomic Gas

We shall here investigate theoretically the intensity of total scattering of X-rays by atoms distributed at random, e. g. , the scattering by the atoms of a monatomic gas. In the scattered radiation we shall not include the characteristic X-rays excited by the incident radiation. The scattered radiation consists then partly of radiation having the same frequency as the incident radiation (coherent scattered radiation) and partly of radiation having other frequencies (incoherent scattered radiation). For sufficiently high frequency of the incident radiation the incoherent scattered radiation is then nearly monochromatic for a given scattering angle, and consists practically entirely of radiation whose wave-length and intensity is given by the formulæ for the Compton effect for the scattering by free electrons. Generally, however, it must be taken into account that several frequencies occur in the scattered radiation for each direction of scattering. The total intensity of the scattered radiation for a given direction has therefore to be taken as a sum of the intensities of the different components, each having a definite frequency. General expressions for the scattered radiation are given by a scattering formula derived by one of us. In this formula “relativity corrections” are neglected; for the intensity of scattering in the Compton effect for free electrons, this approximation, and a further one which we also make, lead to the classical Thomson formula. This means that our intensity formula gives a useful approximation only if the incident radiation is not too hard ( e. g. , has a wave-length not shorter than about 1 Å., in which case the error arising from the approximation just mentioned should not exceed a few per cent.).

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