X-ray facts for kids

An X-ray photograph of a person's lungs.

X-radiation is a kind of electromagnetic radiation. X-rays are waves of X-radiation. X-rays have a shorter wavelength, and therefore more energy, than ultraviolet radiation. They have a much shorter wavelength than visible light (the light that we can see). Radiation with shorter wavelengths (more energy) than the X-ray is called Gamma radiation (γ-rays). These are all parts of the electromagnetic spectrum.

The wavelength of X-rays covers a wide range. Most X-rays have a wavelength in the range of 0.01 to 10 nanometres. This corresponds with frequencies in the range 30 petahertz to 30 exahertz (3×10¹⁶ Hz to 3×10¹⁹ Hz) and energies in the range 100 eV to 100 keV.

X-rays can go through many solid materials. For this reason, taking photograms with X-rays is used in medicine in order to see bones and other things inside the body. Sometimes the term "X-Ray" means these pictures instead of the radiation that makes them.

What these images show will depend on three things: Rayleigh scattering, Compton scattering and photoabsorption. The images show bone because it is dense enough that X-rays are not able to pass through it. Instead, the X-rays are either absorbed or scattered. The images do not show skin and muscle, however, because these tissues are transparent enough for the X-rays to pass through them without being absorbed too much. To detect tumors, other imaging devices are used; such as magnetic resonance imaging. A computed tomography scanner combines an X-ray machine and computer to construct a three dimensional (3D) picture. This has some ability to see other things besides bone.

X-rays are made by hitting metal with fast-moving electrons. They are photons, tiny packets of energy that can move atoms and change chemicals in the body. The things they do depend on the wavelength of the X-rays (or how much energy they have). X-rays with smaller energies ("soft" x-rays) cause the photoelectric effect. Mid-level energies cause Compton scattering. High-level energies ("hard" X-rays) cause pair production. X-rays used for making pictures of people have low to medium energy. Radiation therapy that treats cancer uses Compton scattering and sometimes Pair production.

There are small amounts of X-rays in the air. Like other energy in the air, X-rays can change living cells. Exposing the human body to high doses of X-rays for a long time is dangerous. It can cause cancer. However, cancer cells are hurt more easily, so X-rays are sometimes used to kill them.

Related pages

• X-ray crystallography
• Interventional Radiology

Images for kids

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  Spectrum of the X-rays emitted by an X-ray tube with a rhodium target, operated at 60 kV. The smooth, continuous curve is due to bremsstrahlung, and the spikes are characteristic K lines for rhodium atoms.

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  Head CT scan (transverse plane) slice -– a modern application of medical radiography

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  Abdominal radiograph of a pregnant woman, a procedure that should be performed only after proper assessment of benefit versus risk

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  Using X-ray for inspection and quality control: the differences in the structures of the die and bond wires reveal the left chip to be counterfeit.

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  X-ray fine art photography of needlefish by Peter Dazeley

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  Wilhelm Röntgen

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  Hand mit 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

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  Pulyui's X-ray images

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  Taking an X-ray image with early Crookes tube apparatus, late 1800s. The Crookes tube is visible in center. The standing man is viewing his hand with a fluoroscope screen. The seated man is taking a radiograph of his hand by placing it on a photographic plate. No precautions against radiation exposure are taken; its hazards were not known at the time.

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  1896 plaque published in "Nouvelle Iconographie de la Salpetrière", a medical journal. In the left a hand deformity, in the right same hand seen using radiography. The authors designated the technique as Röntgen photography.

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  A patient being examined with a thoracic fluoroscope in 1940, which displayed continuous moving images. This image was used to argue that radiation exposure during the X-ray procedure would be negligible.

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  Chandra's image of the galaxy cluster Abell 2125 reveals a complex of several massive multimillion-degree-Celsius gas clouds in the process of merging.

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  Dog hip xray posterior view

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  Phase-contrast x-ray image of spider

See also

In Spanish: Rayos X para niños