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Discovery of X-rays The science of x-ray crystallography can be traced back to two major discoveries.  The discovery of x-rays is one of these. 

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The science of x-ray crystallography can be traced back to two major discoveries. 

  • The discovery of x-rays is one of these. 
  • The other, Laue's discovery that crystalline materials can act as diffraction gratings when interacting with electromagnetic radiation of the proper wavelength.
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Discovery of X-Rays

November 1895, Würzburg

Wilhelm Conrad Röntgen

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Cathode ray tubes were known to glow when a current was passed between the cathode and anode.  Röntgen covered his tube with cardboard to darken the room.  This is probably because he was either interested in observing faint fluorescence in materials such as barium platino cyanide or interested in the laws of absorption of "cathdode rays“.  Cahthode rays (electrons) were easily absorbed by the walls of the glass enclosure and air.  So the glow would be faint.

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Röntgen was shocked to note in the darkened room that a barium platino cyanide screen lying on a nearby table (9 feet) showed a flash of fluorescence every time an induction coil discharged into the tube.  This could not be from the easily absorbed cathode rays.

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By the end of the year 1895, Röntgen discovered many properties of his X-rays. 

  • They traveled in a straight line from the point that the cathode rays in the tube struck the glass wall of the tube.
  • They were exponentially absorbed by matter but very much less so than cathode rays.
  • They possessed photographic properties.
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What about Diffraction Effects

Many of the early investigations of X-rays were aimed at finding if they were electromagnetic wave-like phenomenon or particles.  One way one could show wave-like characteristics was to use a suitable "diffraction grating."  The nature of x-ray properties continued until the work of Laue and others such as Thompson, Barkla, and Compton proved that x-rays were electromagnetic phenomena.

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Roentgen and Diffraction

From W. C. Rontgen's Third Communication, March 1897:

'The experiments on the permeability (for X-rays) of plates of constant thickness cut from the same crystal in different orientations, which were mentioned in my first Communication, have been continued. Plates were cut from calcite, quarz, turmaline, beryl, aragonite, apatite and barytes. Again no influence of the orientation on the transparency could be found.

'Ever since I began working on X-rays, I have repeatedly sought to obtain diffraction with these rays; several times, using narrow slits, I observed phenomena which looked very much like diffraction. But in each case a change of experimental conditions, undertaken for testing the correctness of the explanation, failed to confirm it, and in many cases I was able directly to show that the phenomena had arisen in an entirely different way than by diffraction. I have not succeeded to register a single experiment from which I could gain the conviction of the existence of diffraction of X-rays with a certainty which satisfies me.'

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Using the photographic property, he was able to produce photo's of brass weights in a wooden box and, soon thereafter, the first photo of the bones in a living hand (his wife’s).  He also discovered that the output of x-rays could be increased by impinging the cathode rays on a heavy metal "anticathode" which could also be the anode of the tube.  This arrangement is today the basis of the modern x-ray tube.

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The left picture taken at a lecture in January 1896 by Roentgen.  The right by Mr. Haschek and Dr. Lindenthal, in Professor Franz Exner's physicochemical institute in Vienna was obtained by injecting a mixture of lime, cinnabar (mercury) and petroleum in the hand of a cadaver. 

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The photographic use of x-rays advanced quickly. X-ray photographs were used as early as February 1896 in the U.S. to diagnose bone fractures.

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X-ray Shoe Fitting Device

In the late 1940's and early 1950's, the shoe-fitting x-ray unit was a common shoe store sales promotion device and nearly all stores had one.  It was estimated that there were 10,000 of these devices in use. This particular shoe-fitting x-ray unit was produced by the dominant company in the field, the Adrian X-Ray Company of Milwaukee WI, now defunct. Brooks Stevens, a noted industrial designer whose works included the Milwaukee Road Olympian train and an Oscar Meyer Wienermobile, designed this machine.

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The primary component of a shoe-fitting x-ray unit was the fluoroscope which consisted essentially of an x-ray tube mounted near the floor and wholly or partially enclosed in a shielded box and a fluorescent screen. The x-rays penetrated the shoes and feet and then struck the fluorescent screen. This resulted in an image of the feet within the shoes. The fluorescent image was reflected to three viewing ports at the top of the cabinet, where the customer, the salesperson, and a third person (mom) could view the image at the same time. The radiation hazards associated with shoe fitting x-ray units were recognized as early as 1950. The machines were often out of adjustment and were constructed so radiation leaked into the surrounding area.