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.
They are longer than gamma rays but shorter than UV rays. In many languages, X-radiation is called Röntgen radiation after one of its first investigators, Wilhelm Conrad Röntgen.
X-rays are primarily used for diagnostic radiography and crystallography.
Radiographs obtained using X-rays can be used to identify a wide spectrum of pathologies. Due to their short wavelength, in medical applications, X-rays act more like a particle than a wave.
This is in contrast to their application in crystallography, where their wave-like nature is most important.
X-rays span 3 decades in wavelength, frequency and energy. From about 0.12 to 12 keV they are classified as soft x-rays, and from about 12 to 120 keV as hard X-rays, due to their penetrating abilities.
Unit of measure and exposure
The rem is the traditional unit of dose equivalent.
Reported dosage due to dental X-rays seems to vary significantly. Depending on the source, a typical dental X-ray of a human results in an exposure of perhaps, 3, mrems (30 to 9,000 μSv).
How done-medical physics
When medical X-rays are being produced, a thin metallic sheet is placed between the emitter and the target, effectively filtering out the lower energy soft X-rays.
A thin metallic sheet is often placed close to the window of the X-ray tube. The resultant X-ray is said to be hard.
However the distinction between the two terms in medicine depends on the source of the radiation, not its wavelength.
The basic production of X-rays is by accelerating electrons in order to collide with a metal target.
In medical applications, this is usually tungsten or a more crack-resistant alloy of rhenium (5%) and tungsten (95%).
But sometimes molybdenum is used for more specialized applications, such as when soft X-rays are needed as in mammography.
In crystallography, a copper target is most common.
The detection of X-rays is based on various methods. The most commonly known methods are a photographic plate, X-ray film in a cassette, and rare earth screens.
Before computers and before digital imaging, a photographic plate was used to produce radiographic images. Now computed & digital radiography has started to replace film in medicine, though film technology is still used in industrial radiography processes.
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