The study of electromagnetism began in 1820 when Hans Christian Ørsted discovered that electric currents produce magnetic fields (Oersted's law). Light was first linked to electromagnetism in 1845, when Michael Faraday noticed that the polarization of light traveling through a transparent material responded to a magnetic field (see Faraday effect). During the 1860s, James Clerk Maxwell developed four partial differential equations (Maxwell's equations) for the electromagnetic field. Two of these equations predicted the possibility and behavior of waves in the field. Analyzing the speed of these theoretical waves, Maxwell realized that they must travel at a speed that was about the known speed of light. This startling coincidence in value led Maxwell to make the inference that light itself is a type of electromagnetic wave. Maxwell's equations predicted an infinite range of frequencies of electromagnetic waves, all traveling at the speed of light. This was the first indication of the existence of the entire electromagnetic spectrum.
The study of electromagnetism began in 1820 when Hans Christian Ørsted discovered that electric currents produce magnetic fields (Oersted's law) Light was first linked to electromagnetism in 1845 when Michael Faraday noticed that the polarization of light traveling through a transparent material responded to a magnetic field (see Faraday effect) During the 1860s James Clerk Maxwell developed four partial differential equations (Maxwell's equations) for the electromagnetic field Two of these equations predicted the possibility and behavior of waves in the field Analyzing the speed of these theoretical waves Maxwell realized that they must travel at a speed that was about the known speed of light This startling coincidence in value led Maxwell to make the inference that light itself is a type of electromagnetic wave Maxwell's equations predicted an infinite range of frequencies of electromagnetic waves all traveling at the speed of light This was the first indication of the existence of the entire electromagnetic spectrum