EM radiation is classified as being either non-ionizing or ionizing. The bridge between non-ionizing and ionizing radiation occurs within the ultraviolet portion of the EM spectrum, at wavelengths less than 200 nanometers (UVC range). X-rays and gamma rays are best known for their damaging potential.
Non-ionizing radiation has enough energy to move around the atoms in a molecule and/or cause them to vibrate
but not enough energy to cause them to eject any of their electrons.
In contrast, ionizing radiation has so much energy that it can disrupt atomic bonds and eject electrons from the atoms - a process known as ionization.
Ionizing radiation can affect the atoms in living tisses, and so risks damaging tissue and the DNA in genes.
Electromagnetic Radiation
In physics, the term radiation is defined as the emission of energy as electromagnetic waves. The energy associated with EM radiation is directly proportional to frequency and inversely proportional to wavelength. Thus, EM waves with shorter wavelengths and higher frequencies have more energy.
Electromagnetic radiation can be described as a stream of massless particles - photons - traveling in a wave-like pattern at the speed of light (299,792,458 meters/sec).
Non-Ionizing Ionizing