Maxwell's Equations: A Deceptively Short Biography of Electromagnetic Waves

The Re-Collections of Daylight Dreamers: Faraday and MaxwellAri Margolin, HUEN 2130October 15, 2013Maxwells Four Equations

2Sir Isaac Newton in Press

Newtons Discovery of the Refraction of Light (1826) by Pelagio Palagi; Newton (1795) by William Blake.3Michael Faraday In His Laboratory (c. 1850)

Watercolor painting by British artist Harriet Jane Moore; the English painting art of the picturesque. 4La Rgle du jeuNewtonian ModelMomentumForce /Energy (Leibniz; Lagrange)Charge (Coulomb)Corpuscular Theory of LightElectricity and Magnetism separate

Maxwell (Faraday) ModelEnergyChargeMomentumWave Theory of LightLight as EM waveReading FaradayAfter the regular hours of business, [I] was chiefly employed in drawing and copying from the Artist's Repository, a work published in numbers which [I] took in weekly. ... Dr Watts's Improvements of the mind was then read and frequently took in his pocket, when [I] went an early walk in the morning, visiting some other works of art or searching for some mineral or vegetable curiosity. ... [My] mind ever engaged, besides attending to bookbinding which [I] executed in a proper manner. Faraday, 1813.

Annus Mirabilis (1820)rsteds Experiment

Biot-Savart Law (General Case for Ampres Law)

Biot-Savart Law yields the magnetic field given a steady current; the relationship between magnetism and electricity is implicit. Ampres Law, before Maxwell, required symmetry about the central axis of the surface and neglects the effects at the poles of the B field. 7Faradays Apparatus (1831)

Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. No matter how the change is produced, the voltage will be generated. 8On Faradays Law (1831):Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. Lines of Force permeated space.Remembering Youngs Experiment: light travels along these lines!!!!

Time-varying magnetic field induces an electric current.9Youngs Experiment and Transverse Waves (1803)

Of Dreamers and PoetsRouse ye! torpid daylight-dreamers, cast your carking cares away! As calm air to troubled water, so my night is to your day;All the dreary day you labour, groping after common sense,And your eyes ye will not open on the night's magnificence.Ye would scow were I to tell you how a guiding radiance gleamsOn the outer world of action from my inner world of dreams.

--James Clerk Maxwell, Recollections of a Dreamland (1856)

11Maxwell, Defender of FaradayFaraday discovered that when a plane polarized ray traverses a transparent diamagnetic medium in the direction of the lines of magnetic force produced by magnets or currents in the neighborhood, the plane of polarization is caused to rotate.The conception of the propagation of transverse magnetic disturbances to the exclusion of normal ones is distinctly set forth by Professor Faraday in his "Thoughts on Ray Vibrations." The electromagnetic theory of light, as proposed by him, is the same in substance as that which I have begun to develop in this paper, except that in 1846 there were no data to calculate the velocity of propagation.--Maxwell, A Dynamical Theory of the Electromagnetic Field(1865).Lines of Force to the Ether

Transverse waves must travel in a medium.

Maxwell discusses his EM theory in terms of fluid dynamics and specifically adds time component.

Faraday, however, believes EM waves can travel in a vacuum. 13