Charles Barkla

Charles Glover Barkla (1877–1944) was an English physicist who discovered characteristic X-ray radiation and received the 1917 Nobel Prize in Physics.

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X-ray: High-energy electromagnetic radiation with wavelengths shorter than ultraviolet light. Barkla used X-rays to investigate how radiation interacts with matter.
Compton scattering: The inelastic scattering of a photon by a charged particle, accompanied by a change in wavelength. Its wavelength-shifted radiation contrasts with Barkla’s characteristic secondary X-rays.
J. J. Thomson: English physicist who discovered the electron and investigated the conduction of electricity through gases. Barkla conducted his early research under Thomson at the Cavendish Laboratory.
1917 Nobel Prize in Physics: The Nobel Prize in Physics awarded to Charles Glover Barkla for his discovery of characteristic Röntgen radiation. The award recognized the discovery at the center of Barkla’s career.
X-ray scattering: The deflection of X-rays when they interact with matter. Barkla studied scattered X-rays before identifying their characteristic components.
Fluorescence: Light emitted by a substance after it absorbs radiation, typically at a longer wavelength. Barkla described characteristic X-ray emission as a form of X-ray fluorescence.
Ernest Rutherford: New Zealand-born physicist who established the nuclear model of the atom and studied radioactivity. Rutherford’s research on radiation and atoms formed part of Barkla’s scientific milieu.
X-ray crystallography: A method that uses X-ray diffraction to determine the atomic structure of crystals. It grew into a major structural method alongside the atomic spectroscopy Barkla advanced.
Characteristic X-ray: An X-ray emitted at energies characteristic of the element whose atoms produce it. This is the radiation Barkla discovered and linked to particular elements.
Polarization: The orientation of a wave’s oscillations, restricted to a direction or plane. Barkla used polarized scattered X-rays to show that X-rays are transverse waves.