Radiation
Non-ionizing radiation, continued.
The upper part of the sketch shows the visible part of the spectrum, and also the near-visible portions you are familiar with, infrared that warms you, and ultraviolet that gives you a sun tan and increases your chances of skin cancer. (The sketch gives the wave length in angstroms, a seldom used unit these days, but which is a tenth of a nanometer. Anyhow the scale goes from one tenth of a micrometer to one micrometer.) Note that the near visible portion is then funneled down into the entire spectrum, of which it is only a small portion.
The scale on top is the frequency in cycles per second, today called Hertz, while the scale at the bottom is the wave length, with the length units indicated in meters. Note that the longer wavelengths have slower frequencies. Household electric is 60 Hz, what is its wavelength . Now off to the left are some very high frequency (and very short wavelength) electromagnetic radiation, x-rays and gamma rays, that are strong enough to knock electrons from atoms and make ions out of them. So these forms of electromagnetic radiation are also forms of ionizing radiation. All the radiation to the right of these are non-ionizing radiation.