The electromagnetic spectrum encompasses all electromagnetic radiation and classifies it according to its energy, and hence its frequency, which ranges from the shortest wavelength (higher frequency) radiation, such as gamma rays and x-rays, followed by ultraviolet light, visible light and infrared rays, to electromagnetic waves of greater wavelength (less frequency), such as radio waves. In addition to the division into the indicated major bands, based on the ability to interact with matter, electromagnetic radiation can be divided into ionizing and non-ionizing.