Summary
This 1911 monograph by Charles Glover Barkla presents his experimental findings that X-rays, when scattered by matter, exhibit properties of transverse electromagnetic waves, and that each element emits characteristic X-ray radiation with a unique penetrating power. Barkla’s central thesis is that these characteristic radiations arise from the atomic structure of the element, specifically from electrons within the atom, and that their absorption and scattering behaviors follow predictable laws. The book details his systematic measurements of X-ray scattering from gases and solids, demonstrating that the intensity of scattered X-rays depends on the atomic weight of the scatterer and the angle of observation. Barkla also identifies two distinct types of characteristic radiation—K-series and L-series—for elements, establishing that these are independent of chemical combination and thus intrinsic to the atom. A reader takes away a foundational understanding of how X-ray scattering and characteristic emissions reveal atomic structure, laying groundwork for later quantum theory and Moseley’s law.
Key concepts
- Characteristic X-radiation — X-rays emitted by an element when its atoms are excited, having a specific penetrating power unique to that element.
- K-series and L-series — Two distinct sets of characteristic X-ray lines, with the K-series being more penetrating and associated with inner atomic electrons.
- Scattering coefficient — A measure of how much X-ray intensity is reduced when passing through a material, dependent on the atomic weight and density of the scatterer.
- Polarization of scattered X-rays — The phenomenon where scattered X-rays are partially polarized, confirming their transverse wave nature.
- Absorption edge — A sharp discontinuity in the absorption of X-rays by an element at a specific wavelength, corresponding to the energy needed to eject an inner electron.
From the book
Title: The Scattering of X-Rays and the Characteristic Radiations of Elements by Charles Glover Barkla
For other versions of this work, see Encyclopædia Britannica . ← 1911 Encyclopædia Britannica ( 1911 ) Title page → related portals : Reference Works Shortcut : EB11 or EB1911 Notes on reading the Wikisource edition . A special disclaimer for this project . Collaboration page for contributors . 12543 1911 Encyclopædia Britannica 1911 Table of contents This work is in the public domain in the United States because it was published before January 1, 1931. This work may be in the public domain in countries and areas with longer native copyright terms that apply the rule of the shorter term to foreign works . Public domain Public domain false false← Alabama 1911 Encyclopædia Britannica , Volume 1 "Alabama" Arbitration by Montague Hughes Crackanthorpe Alabama River → See also Alabama Claims on…
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