In 1894, Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this invisible, radiant energy. However, he did not work with actual X-rays. He based it on the electromagnetic theory of light. He postulated a dispersion theory before Röntgen made his discovery and announcement. Helmholtz formulated mathematical equations for X-rays. In 1889, Ukrainian-born Ivan Puluj, a lecturer in experimental physics at the Prague Polytechnic who since 1877 had been constructing various designs of gas-filled tubes to investigate their properties, published a paper on how sealed photographic plates became dark when exposed to the emanations from the tubes. It has been suggested that at least some of these "Lenard rays" were actually X-rays. He measured the penetrating power of these rays through various materials. He found that something came through, that would expose photographic plates and cause fluorescence. He built a Crookes tube with a "window" at the end made of thin aluminium, facing the cathode so the cathode rays would strike it (later called a "Lenard tube"). Starting in 1888, Philipp Lenard conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air. His letter of Janu(describing his discovery as "electric photography") to the Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner. From 1886 to 1888, he had studied in the Hermann von Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as previously studied by Heinrich Hertz and Philipp Lenard. When Stanford University physics professor Fernando Sanford created his "electric photography", he also unknowingly generated and detected X-rays. This work was further explored by Humphry Davy and his assistant Michael Faraday. In 1785, he presented a paper to the Royal Society of London describing the effects of passing electrical currents through a partially evacuated glass tube, producing a glow created by X-rays. The earliest experimenter thought to have (unknowingly) produced X-rays was William Morgan. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube. Crookes tubes created free electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. Many of the early Crookes tubes (invented around 1875) undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below. They were noticed by scientists investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in 1869. History Pre-Röntgen observations and research Įxample of a Crookes tube, a type of discharge tube that emitted X-raysīefore their discovery in 1895, X-rays were just a type of unidentified radiation emanating from experimental discharge tubes. X-rays are also used in ways such as checking for broken bones, detecting certain kinds of diseases, "identification of some metals", and ascertaining the locations of weak points in steel. Spellings of X-ray(s) in English include the variants x-ray(s), xray(s), and X ray(s). He named it X-radiation to signify an unknown type of radiation. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it on November 8, 1895. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz ( 3 ×10 16 Hz to 3 ×10 19 Hz) and energies in the range 145 eV to 124 keV. Note the edges of hollow cylinders as compared to the solid candle.Īn X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Natural color X-ray photogram of a wine scene.
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