The radiation used for product and food irradiation is known as ionizing radiation. Radiation is all around us, part of what is known as the electromagnetic spectrum. This spectrum includes radio waves, heat in the form of infrared radiation, microwaves and even the light that allows us to see the world around us. Ultraviolet rays, x-rays and even gamma radiation are all a part of this electromagnetic spectrum. Radio waves have very long wavelengths, low frequency and hence, low energy.
Microwaves have higher energy, and x-rays and gamma rays have the highest.
When an atom, the fundamental building block of all matter, is irradiated by higher wavelength forms of energy, the atom is changed by knocking an electron from it. The atom then becomes an ion. This ion is not radioactive, but is different from the original atom. But there is no question that the irradiation process changes the atoms of the product being irradiated. All organisms are made up of atoms and molecules.