Röntgenstrahls

Röntgenstrahlen (X-rays) are a form of high-energy electromagnetic radiation that can penetrate several materials, with absorption varying by density and composition. They were discovered in 1895 by Wilhelm Conrad Röntgen, who observed faint fluorescence from a coated screen while experimenting with a cathode ray tube. He named the radiation X-rays to denote the unknown form of radiation. The discovery led to rapid development in science and medicine.

X-rays are produced when high-energy electrons decelerate upon striking a dense target (typically tungsten) in a vacuum tube. The emitted spectrum includes Bremsstrahlung radiation, which covers a broad range of energies, and characteristic X-rays, which arise from inner-shell transitions of the target atoms. The resulting photons have wavelengths primarily in the range of about 0.01 to 10 nanometers and energies suitable for penetrating human tissue.

Applications include medical imaging (radiography, fluoroscopy, computed tomography), industrial nondestructive testing, security screening, and, at higher energies, therapeutic radiotherapy. In medicine, X-rays allow visualization of bones and many soft tissues when contrasted appropriately.

Safety: X-rays are ionizing radiation and pose stochastic and deterministic risks at sufficiently high doses. Protection relies on minimizing exposure, shielding with lead, and using the lowest effective dose. Dose is monitored in modern practice by standardized quantities; the roentgen was historically used as an exposure unit, but modern practice uses coulombs per kilogram for exposure and gray and sievert for dose.