Overview of X-rays
About 2 min read
X-rays are a form of electromagnetic radiation with very short wavelengths and high energy. Their wavelengths range from about 0.01 to 10 nanometers, corresponding to frequencies of roughly 3 × 1016 to 3 × 1019 hertz and energies of about 100 electronvolts to 100 kiloelectronvolts. This places them between ultraviolet light and gamma rays on the electromagnetic spectrum.
Because they can pass through soft tissue but are blocked by denser material such as bone, X-rays became one of the most important tools in medicine and industry.
Questions you may have include:
- How were X-rays discovered?
- How are X-rays produced?
- What are X-rays used for?
Discovery of X-rays
X-rays were discovered on November 8, 1895, by the German physicist Wilhelm Conrad Roentgen while he was studying the glow produced by electricity passing through a low-pressure gas tube. He noticed that a coated screen some distance away glowed even when the tube was shielded, meaning an invisible radiation was passing through the air. Not knowing its nature, he called it “X” radiation. He soon produced a photograph of the bones in a human hand, and for this work he received the first Nobel Prize in Physics in 1901. Additional reader questions are answered in the lesson on X-rays.
How X-rays are produced
X-rays are generated when fast-moving electrons strike a metal target. As the electrons are suddenly slowed by the atoms of the target, they give off energy as X-rays. A second source comes from electrons knocking inner electrons out of the target’s atoms, which produces X-rays at specific energies characteristic of that metal. Both effects occur together in an X-ray tube.
Properties and uses
X-rays travel in straight lines, are not bent by magnetic or electric fields, and are a form of ionizing radiation, meaning they carry enough energy to remove electrons from atoms. They penetrate materials to a degree that depends on the material’s density, which is why they reveal bones inside the body and flaws inside metal parts. Common uses include medical and dental imaging, treatment of some cancers, security screening, and the study of crystal structures. Because they are ionizing, exposure is kept as low as reasonably possible.
Summary
X-rays are high-energy electromagnetic radiation discovered by Wilhelm Roentgen in 1895. They are produced when fast electrons strike a metal target, penetrate soft tissue while being blocked by denser material, and are widely used in imaging, medicine, security, and materials science. As a form of ionizing radiation, they are handled with care to limit exposure.