Frequencies
Non-ionizing radiation (NIR) is a generic term used to describe electromagnetic radiation that does not carry enough photon energy to ionize atoms or molecules and includes mechanical waves in the low and high frequency range (infra- and ultrasound).
Non-ionizing radiation is sub-grouped into frequencies (number of oscillation per second) or wavelength bands (distance between two peaks of an oscillation). This classification is not always used strictly and might differ depending on the information source. ICNIRP uses subcategories of NIR, that group frequencies or wavelength bands together, and treats these groupings separately in terms of protection, mainly because the frequencies or wavelengths of the NIR in each grouping have different actions on the tissues.