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Tuesday, January 5, 2010

X-Rays day

 
First X-Ray
image from: esrf.eu
X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 3 × 1016 Hz to 3 × 1019 Hz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays. In many languages, X-radiation is called Röntgen radiation after Wilhelm Conrad Röntgen, who is generally credited as their discoverer, and who had called them X-rays to signify an unknown type of radiation.
Wilhelm Conrad Röntgen is usually credited as the discoverer of X-rays 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", though many referred to these as "Röntgen rays" for several decades after their discovery.
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 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.
 
font: wikipedia (click to see full article)
Versão Portuguesa: Raios X
Versión Española:  Rayos X
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