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The Electromagnetic Spectrum and Photon Energy
Shorter wavelength means higher frequency and more photon energy. X-rays and gamma rays sit at the ionizing end of the spectrum.
The spectrum
Electromagnetic (EM) energy travels as linked electric and magnetic fields. Every type moves at the speed of light, 3 × 10⁸ m/s, and has no mass or charge. The EM spectrum orders the types from longest to shortest wavelength: radio, microwave, infrared, visible light, ultraviolet (UV), x-rays and gamma rays. Only the short-wavelength end is ionizing, meaning a single photon has enough energy to remove an electron from an atom. That end includes high-energy UV, x-rays and gamma rays. Radio waves, microwaves, infrared and visible light are nonionizing. They can warm tissue, but a single photon cannot ionize an atom.