electromagnetic

Electromagnetic refers to phenomena related to electricity and magnetism and to the electromagnetic field that pervades space. In physics, electromagnetism is one of the four fundamental interactions, governing how electric charges and currents generate electric and magnetic fields, how those fields interact with matter, and how energy and information propagate through space via electromagnetic waves.

The modern theory emerged from 19th-century experiments and the work of James Clerk Maxwell, who unified electricity, magnetism, and light. Maxwell's equations describe how changing electric and magnetic fields produce each other and how they excite propagating waves. In vacuum, these waves travel at the speed of light, c, establishing a deep link between optics and electromagnetism.

Electromagnetic radiation spans a broad spectrum, from radio waves and microwaves to infrared, visible light, ultraviolet, X-rays, and gamma rays. Electromagnetic waves are oscillations of electric and magnetic fields that travel through space; their energy is carried by photons in quantum terms. The spectral range determines how waves interact with matter and their practical uses.

The electromagnetic force underpins a wide range of technologies, including electrical power generation, transmission, and motors; radio, television, and mobile communications; radar; and a variety of imaging and sensing techniques. The interaction of electromagnetic radiation with atoms and molecules enables spectroscopy, microscopy, and medical diagnostics.

In quantum theory, the electromagnetic field is quantized as photons, the force carrier of electromagnetism. The field is described by gauge symmetry and quantum electrodynamics, which provides highly accurate predictions for atomic and subatomic processes, forming the basis for much of modern physics and engineering.