Electromagnetic waves carry electromagnetic energy, also known as electromagnetic radiation, through matter, empty space, momentum and angular momentum. Depending on their frequency and wavelength, electromagnetic waves create different types of phenomena, including visible light, infrared radiation, ultraviolet radiation, radio waves, gamma rays, x-rays and microwaves.
Visible light is created by electromagnetic waves with a wavelength between 400 and 700 nanometers, but these numbers only approximate the visible light wavelength range. Humans use electromagnetic radiation for a variety of purposes, including sending radio signals, performing x-rays, using infrared detection, vision, heating food and sterilization.
According to the quantum theory of electromagnetism, electromagnetic waves consist of the oscillations of traveling photons, the tiny particles that electromagnetic energy is composed of. Photons display wave-particle duality, meaning that they show characteristics of both waves and particles. The synchronized oscillations of electromagnetic waves travel and carry energy at the speed of light.
While electromagnetic waves do not have mass, they still experience the effects of gravity. The crests and troughs of the wave frequency vary in size and are inversely proportional to the wavelength. Electromagnetic waves may be the size of a building, such as is the case with radio waves, or they may be incredibly small, as in the case of gamma rays.