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Michael Faraday holding a piece of glass of the type he used to demonstrate the effect of magnetism on polarization of light, c. 1857.. By 1845, it was known through the work of Augustin-Jean Fresnel, Étienne-Louis Malus, and others that different materials are able to modify the direction of polarization of light when appropriately oriented, [4] making polarized light a very powerful tool to ...
In 1845, Faraday discovered that many materials exhibit a weak repulsion from a magnetic field: an effect he termed diamagnetism. [ 65 ] Faraday also discovered that the plane of polarization of linearly polarised light can be rotated by the application of an external magnetic field aligned with the direction in which the light is moving.
The electromagnetic theory of light adds to the old undulatory theory an enormous province of transcendent interest and importance; it demands of us not merely an explanation of all the phenomena of light and radiant heat by transverse vibrations of an elastic solid called ether, but also the inclusion of electric currents, of the permanent ...
Michael Faraday discovered the converse, that magnetism could induce electric currents, and James Clerk Maxwell put the whole thing together in a unified theory of electromagnetism. Maxwell's equations further indicated that electromagnetic waves existed, and the experiments of Heinrich Hertz confirmed this, making radio possible.
He shows that a coil of wire carrying a current behaves like an ordinary magnet and suggests that electromagnetism might be used in telegraphy. He mathematically develops Ampère's law describing the magnetic force between two electric currents. His mathematical theory explains known electromagnetic phenomena and predicts new ones.
Maxwell's theory predicted that coupled electric and magnetic fields could travel through space as an "electromagnetic wave". Maxwell proposed that light consisted of electromagnetic waves of short wavelength, but no one had been able to prove this, or generate or detect electromagnetic waves of other wavelengths. [15]
The magnetic field (marked B, indicated by red field lines) around wire carrying an electric current (marked I) Compass and wire apparatus showing Ørsted's experiment (video [1]) In electromagnetism , Ørsted's law , also spelled Oersted's law , is the physical law stating that an electric current induces a magnetic field .
1820 - Hans Christian Ørsted discovers electric currents create magnetic effects. André-Marie Ampère deduces that magnetism is basically the force between electric currents. 1833 - Carl Friedrich Gauss and Wilhelm Weber worked out the mathematical theory for separating the inner and outer magnetosphere sources of Earth's magnetic field.