According to the Encyclopedia Britannica, in terms of classical theory, electromagnetic radiation refers to energy that flows at the universal speed of light via free space or a material medium in the form of electric and magnetic fields that comprise electromagnetic waves, such as radio waves, gamma rays and visible light. Electromagnetic waves are characterized by their intensity and the frequency of the electric and magnetic field's time variation.
Nearly 0.01 percent of the mass or energy of the universe exists in the form of electromagnetic radiation, the Encyclopedia Britannica elaborates. All living things on Earth rely on the electromagnetic radiation provided by the sun. Humans depend on its various forms, particularly for the provision of medical services and communications technology. Man-made electromagnetic radiation also pervades human life. For instance, broadcasting stations transmit electromagnetic waves to television sets, and heaters give off infrared waves that provide warmth. Radar waves guide airplanes, and microwave ovens use electromagnetic waves to heat food.
The Lawrence Berkeley National Laboratory explains that the motion of electrically charged particles produces electromagnetic waves, which are also known as electromagnetic radiation, as they radiate from the electrically charged particles. These waves travel through empty space, through air and through other substances. Scientists say that electromagnetic radiation acts like waves and also acts like a stream of particles, called photons, that do not have mass.