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How did James Clerk Maxwell connect electricity, magnetism, and light?

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Learn about magnetic fields and the levels of particles, atoms, crystals, and domains — magnet Magnetic fields and the levels of magnetism of particles, atoms, crystals, and domains.

James Clerk Maxwell unified the fields of electricity, magnetism, and optics by developing a comprehensive mathematical theory of electromagnetism in the 1860s.5

Building upon the experimental work of predecessors like Michael Faraday, Maxwell formulated a set of equations that described the interrelation of electric and magnetic fields. To ensure these equations were logically consistent, he introduced the concept of "displacement current," which accounted for changing electric fields.123

When Maxwell combined these equations, he derived a wave equation indicating that transverse electric and magnetic disturbances propagate as waves. He calculated the velocity of these waves using electrical measurements previously established by Wilhelm Eduard Weber and Rudolf Kohlrausch. The resulting value matched the known speed of light in a vacuum, leading Maxwell to the profound conclusion that light is a form of electromagnetic radiation. This theoretical breakthrough was later confirmed experimentally by Heinrich Hertz in 1886.3245