X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (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 and longer than gamma rays. In many languages, X-radiation is called Röntgen radiation, after Wilhelm Conrad Röntgen, who is usually credited as its discoverer, and who had named it X-radiation to signify an unknown type of radiation. Correct spelling of X-ray(s) in the English language includes the variants x-ray(s) and X ray(s). XRAY is used as the phonetic pronunciation for the letter x.continue..
All light and radio waves belong to the electromagnetic spectrum, and are all considered different types of electromagnetic waves, including: microwaves and infrared bands whose waves are longer than those of visible light (between radio and the visible) and UV, EUV, X-rays and g-rays (gamma rays) with shorter wavelengths. The electromagnetic nature of x-rays became evident when it was found that crystals bent their path in the same way as gratings bent visible light: the orderly rows of atoms in the crystal acted like the grooves of a grating.continue..

As with many of mankind's monumental discoveries, X-ray technology was invented completely by accident. In 1895, a German physicist named Wilhelm Roentgen made the discovery while experimenting with electron beams in a gas discharge tube. Roentgen noticed that a fluorescent screen in his lab started to glow when the electron beam was turned on. This response in itself wasn't so surprising -- fluorescent material normally glows in reaction to electromagnetic radiation -- but Roentgen's tube was surrounded by heavy black cardboard. Roentgen assumed this would have blocked most of the radiation.continue..

An important source of X rays is synchrotron radiation. X rays are also produced in a highly evacuated glass bulb, called an X-ray tube, that contains essentially two electrodes—an anode made of platinum, tungsten, or another heavy metal of high melting point, and a cathode. When a high voltage is applied between the electrodes, streams of electrons (cathode rays) are accelerated from the cathode to the anode and produce X rays as they strike the anode.continue..

X-rays are just like any other kind of electromagnetic radiation. They can be produced in parcels of energy called photons, just like light. There are two different atomic processes that can produce x-ray photons. One is called Bremsstrahlung, which is a fancy German name meaning "braking radiation." The other is called K-shell emission. They can both occur in heavy atoms like tungsten. continue..

X-rays are essential medical tools for doctors. However, the prevalence of new technology and the risks associated with X-rays have caused many health professionals to re-think the their use. X-rays are ionized forms of radiation that penetrate living tissue. Doctors found they could use X-rays and imaging technology to give a detailed view of a patient's skeletal system and some tissues. X-rays are still used today, however, alternative imaging technologies such as Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans are now gaining popularity in the medical community. continue..

Modern medical X-ray machines have been grouped into two categories: those that generate "hard" X-rays and those that generate "soft" X-rays. Soft X-rays are the kind used to photograph bones and internal organs. They operate at a relatively low frequency and, unless they are repeated too often, cause little damage to tissues. Hard X-rays are very high frequency rays. They are designed to destroy the molecules within specific cells, thus destroying tissue. Hard X-rays are used in radiotherapy, a treatment for cancer. The high voltage necessary to generate hard X-rays is usually produced using cyclotrons or synchrotrons. These machines are variations of particle accelerators (atom smashers).continue..

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