The Electromagnetic Spectrum, which goes by either (EMS) or, depending on context (ES), defines the available ranges of all frequencies of Electromagnetic Radiation (EMR) or (ER). The spectrum ranges from exceptionally low frequencies, such as those used for radio waves, to high frequencies, such as gamma rays.

Electromagnetic radiation can be divided into several categories based on its frequency. These categories include radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Each category has unique properties and uses.

Radio waves are the lowest frequency category of electromagnetic radiation. They are used for communication, such as AM/FM radio and television broadcasts. Microwaves are slightly more frequent than radio waves and are used for RADAR and cell phone signals. Infrared Radiation is even higher in frequency than microwaves and is invisible to the human eye but can be felt as heat energy.