Definition and electromagnetic spectrum placement

Summary

An X-ray is a form of high-energy electromagnetic radiation whose wavelength is shorter than ultraviolet light but longer than gamma rays. It is typically described as having wavelengths from about 10 nanometers to 10 picometers, corresponding to frequencies roughly from 30 petahertz to 30 exahertz, and photon energies from about 100 eV to 100 keV. X-rays were discovered in 1895 by Wilhelm Conrad Röntgen, who named the radiation “X” to indicate it was an unknown type at the time. Because X-rays can penetrate many solid materials—including construction materials and living tissue—they are widely used for imaging, such as in medical radiography and in materials science. However, X-rays are ionizing radiation, so exposure can be hazardous and is strictly controlled due to risks such as DNA damage, cancer, and burns at higher intensities.

Key Points

• 1

  X-rays are electromagnetic radiation positioned between ultraviolet and gamma rays in the electromagnetic spectrum.

• 2

  Typical X-ray wavelengths are about 10 nm to 10 pm, with photon energies roughly 100 eV to 100 keV.

• 3

  X-rays were discovered in 1895 by Wilhelm Conrad Röntgen and named “X” for an unknown radiation type.

• 4

  X-rays penetrate many materials, enabling imaging uses, but they are ionizing and can be hazardous, requiring strict control.