scholarly journals Absorption Measurements of Certain Changes in the Average Wave-Length of Tertiary X-Rays

1924 ◽  
Vol 10 (5) ◽  
pp. 196-199 ◽  
Author(s):  
S. K. Allison ◽  
W. Duane
Keyword(s):  
Wave Length ◽  
X Rays ◽  
Average Wave ◽  
Absorption Measurements

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.

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.

Average Wave Lengths of X-rays

Radiology ◽  
1924 ◽  
Vol 3 (4) ◽  
pp. 328-334
Author(s):  
A. Mutscheller
Keyword(s):  
X Rays ◽  
Average Wave

XXVII.—A Colour-Vision Spectrometer

1926 ◽  
Vol 45 (3) ◽  
pp. 302-307
Author(s):  
W. Peddie
Keyword(s):  
Blue Light ◽  
Focal Plane ◽  
Colour Vision ◽  
Wave Length ◽  
Established Fact ◽  
Average Wave ◽  
Collimating Lens

It is now a thoroughly well-established fact that a satisfactory match to any coloured light observable in nature can be made by a combination, in suitable proportions, of three standard lights suitably chosen from a spectrum. It is customary to choose for the standards a red, a green, and a blue light of definite average wave-length in each case. The greatest deviation from the average is made so slight that there is no visible difference in colour between the extreme components present in any one standard. A simple way (used by Maxwell) of obtaining these standards would be by means of an ordinary spectroscopic arrangement in which light is focussed on a slit, and is parallelised by a collimating lens, after which it passes through a prism and the object glass of a telescope, on whose focal plane a spectrum is thus formed.

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.

scholarly journals The diffraction of cathode rays by thin celluloid films

1928 ◽  
Vol 119 (783) ◽  
pp. 663-667 ◽  
Keyword(s):  
Thin Film ◽  
Phase Velocity ◽  
Multiple Scattering ◽  
Photographic Plate ◽  
Wave Length ◽  
Normal Incidence ◽  
X Rays ◽  
Series Of Experiments ◽  
Diffraction Patterns ◽  
Moving Particle

In the de Broglie theory of mechanics a moving particle behaves as a group of waves of wave-length = h √¯1 — v 2 / c 2 / m 0 v and phase velocity V = c 2 / v , where m 0 is the mass of the particle, v its speed and c the velocity of light. In the case of electrons of energy 10,000 to 40,000 volts, the corresponding wave­ lengths would be from 1·22 X 10 -9 to 0·66 X 10 -9 cms. These waves, there­ fore, should behave in many ways like hard X-rays, and, in particular, should show similar diffraction patterns when passed through crystals. Thus, accord­ing to the Bragg formula, if the rays are incident at an angle θ on a set of parallel planes, we should get reflection provided that 2 d sin θ = nλ,d being the spacing between the planes. To investigate these effects, a series of experiments, suggested and super­vised by Prof. G. P. Thomson, was begun in October, 1926. An account of these has already been published in ‘ Nature,’ but since then much more accurate work has been done. The experiments consisted in sending a beam of homogeneous cathode rays through a thin film at normal incidence and receiving them on a photographic plate. As shown below, the resultant pattern should be of the Hull-Debye-Scherrer type. Celluloid was chosen because it is comparatively easy to get films of the order of 500 Ă. U. thick. These were pre­pared by dissolving celluloid in amyl acetate. A little of the solution was dropped on water and the amyl allowed to evaporate. The celluloid which remained was removed on cardboard frames. It is essential that the films be thin enough to prevent blurring of the pattern by multiple scattering.

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