German physicist Wilhelm
Röntgen is usually credited as the discoverer of X-rays in 1895, because he was
the first to systematically study them, though he is not the first to have
observed their effects. He is also the one who gave them the name
"X-rays" (signifying an unknown quantity) though many others referred
to these as "Röntgen rays" (and the associated X-ray radiograms as,
"Röntgenograms") for several decades after their discovery and even
to this day in some languages, including Röntgen's native German.
Handmit
Ringen (Hand with Rings): print of Wilhelm Röntgen's first
"medical" X-ray, of his wife's hand, taken on 22 December 1895 and
presented to Ludwig Zehnder of the Physik Institut, University of Freiburg,
on 1 January 1896.
X-rays were found emanating
from Crookes tubes, experimental discharge tubes invented around 1875, by
scientists investigating the cathode rays, that is energetic electron beams,
that were first created in the tubes. 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. 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. Many of the early Crookes tubes undoubtedly radiated
X-rays, because early researchers noticed effects that were attributable to
them, as detailed below. Wilhelm Röntgen was the first to systematically study
them, in 1895.
