What Is an X-ray?

What Is an X-ray?

An x-ray is a discrete bundle of electromagnetic energy called a photon. In that regard, it is similar to other forms of electromagnetic energy such as light, infrared, ultraviolet, radio waves, or gamma rays. The associated electromagnetic energy can be thought of as oscillating electric and mag-netic fields propagating through space at the speed of light. The various forms of electromagnetic energy differ only in frequency (or wavelength). However, because the energy carried by each photon is proportional to the frequency (the proportionality constant is called Planck’s constant), the higher frequency x-ray or gamma ray photons are much more energetic than, for example, light photons and can readily ionize the atoms in materials on which they im-pinge. The energy of a light photon is of the order of one electron-volt (eV), whereas the average energy of an x-ray photon in a diagnostic x-ray beam is on the order of 30 kiloelectron volts (keV) and its wavelength is smaller than the diameter of an atom (10 ⁸ cm).

In summary, an x-ray beam can be thought of as a swarm of photons traveling at the speed of light, each photon repre-senting a bundle of electromagnetic energy.