An electromagnetic wave is a type of energy that travels through space in the form of vibrating electric and magnetic fields. When a charged particle accelerates or vibrates, it creates a disturbance in the electric field around it. This disturbance propagates through space at the speed of light, and as it does so, it also creates a disturbance in the magnetic field. The electric and magnetic fields are perpendicular to each other, and they travel together through space in the form of a wave.

The wavelength of an electromagnetic wave is the distance between two adjacent peaks or troughs of the wave, and the frequency of the wave is the number of peaks or troughs that pass a given point in space each second. The speed of an electromagnetic wave is equal to the product of its wavelength and its frequency.

Electromagnetic waves include a wide range of frequencies, from extremely low frequencies (ELF) to extremely high frequencies (EHF). ELF waves have wavelengths that are longer than 10 kilometers, while EHF waves have wavelengths that are shorter than 1 millimeter. The human eye can only see electromagnetic waves with wavelengths between about 400 and 700 nanometers, which is the visible spectrum.

Electromagnetic waves are used for a variety of purposes, including communication, navigation, and medical imaging. Radio waves are used for AM and FM radio broadcasting, as well as for cell phones and Wi-Fi. Microwaves are used for cooking food, heating homes, and communicating with satellites. Infrared waves are used for night vision goggles, thermal imaging, and remote controls. Ultraviolet waves are used for tanning beds, sunlamps, and water purification. X-rays are used for medical imaging and security screening. Gamma rays are used for cancer treatment, food preservation, and industrial radiography.