Wilhelm Röntgen


In 1901 Wilhelm Conrad Röntgen (or Roentgen) was the recipient of the first Nobel Prize in physics, awarded to him "in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him." The "remarkable rays" Röntgen called x rays (for want of a better name), but in Germany they very quickly came to be called Röntgen rays. A very shy man, Röntgen declined to give the customary acceptance speech at the awards ceremony.

Röntgen's critical discovery was made in 1895 when he happened to observe that, as a cathode-ray tube was being operated in a darkened room, paper covered with barium platinocyanide lying some distance from the tube "lit up with brilliant fluorescence." The fluorescence of barium platinocyanide was used at that time to establish the presence of invisible rays of the solar spectrum (such as ultraviolet). However, on this occasion, the tube had been surrounded by a close-fitting shield of black cardboard, quite opaque to ultraviolet light or sunlight.

With further experimentation Röntgen learned that the fluorescent screen lit up when it was placed "behind a book of a thousand pages" or "behind two packs of cards." Similarly, tinfoil, blocks of wood, and glass (as long as it contained no lead) offered little resistance to the enigmatic radiation. Moreover, "if a hand be held before the fluorescent screen, the shadow shows the bones darkly, with only faint outlines of the surrounding tissues." Röntgen soon found that his x rays darkened a photographic plate. One of his first x-ray photographs revealed the bone structure of his wife's hand.

When Röntgen first published his results, the macabre revelation of living bone structures created a sensation, and within a month articles on the value of x rays within medicine appeared in major medical journals. x rays have been an invaluable tool in medicine, dentistry, and industry ever since. A roentgen, abbreviated as R, is the international unit of quantity or dose for both x rays and gamma rays. It is equal to the amount of x or gamma radiation that produces as a result of ionization one electrostatic unit of charge in one cubic centimeter (0.034 ounces) of dry air.

Röntgen was born in Lennap, Germany, in 1845, but his family shortly thereafter moved to Holland. At age sixteen, he entered the Utrecht Technical School, where he remained for three years. He then moved to the Polytechnic Institute in Zurich, where he earned a diploma as a mechanical engineer in 1868 and a Ph.D. degree a year later. He became an assistant to the physicist August Kundt, whom he accompanied to the University of Würzburg in 1871, and then to the University of Strasbourg. The volume of his research output at this time resulted in his being offered the chair of physics at the University of Giessen in Hesse, where he resided from 1879 until 1888. In 1888 he returned to the University of Würzburg as professor of physics and director of its Physical Institute. It was here that he made his momentous discovery of x rays. In 1900 he moved to the University of Munich, from which he retired in 1920. He died in 1923, aged seventy-seven.

SEE ALSO Radiation .

Keith L. Manchester


Röntgen, Wilhelm (1896). "On a New Kind of Rays." Nature 53: 274–276.

Seliger, H. H. (1995). "Wilhelm Conrad Röntgen and the Glimmer of Light." Physics Today 48: part 11, pp. 25–31.

Internet Resources

The Nobel Prize Internet Archive. Information available from http://almaz.com/nobel/physics/1901a.html .

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