Augustin Jean Fresnel Biography

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World of Physics on Augustin Jean Fresnel

At the onset of the nineteenth century, the most widely accepted belief among physicists was that light was a particle that traveled through ether, an invisible substance that made up the heavens. Soon after the turn of the century, however, came the revival of an old belief; that light was actually a wave that needed no medium for travel. The debate that arose among scientists was furious, and there were few more successful spokesmen for the wave theory than Augustin Fresnel.

The son of an architect, Fresnel was born in Normandy in 1788. His future as a scientist was by no means obvious--in fact, Fresnel was eight before he learned to read. He entered the École Polytechique in Paris in 1804, with plans to pursue a career in engineering. After three more years, he became a civil engineer, working for the government for most of his adult life.

Fresnel's interest in optics began under unusual circumstances. In 1814, while he was working on the imperial highway, France's political stability was threatened by Napoleon's return from exile. Seeing this as an attack on civilization, Fresnel abandoned his position with the government to assist the opposing Royalist forces under Louis XVIII. Subsequently, he was suspended and put under police surveillance. During this time, Fresnel furthered his budding theories concerning light, duplicating several experiments Thomas Young had developed a decade earlier. Soon after, Napoleon was defeated at Waterloo and Fresnel was welcomed back, but his brief diversion had planted within him a firm belief in the wave nature of light and an obsession with expanding his own ideas into a comprehensive mathematical theory.

Until 1824, Fresnel's studies advanced almost without interruption, and he was aided by several government appointments to Paris, where he conducted the bulk of his research during this time. The steadfastness with which he attacked his subject was founded upon a few maxims: Fresnel believed, foremost, that for a theory to be true in nature it must be simple and in agreement with both experience and experiment. Nature itself, he believed, aims at producing varied effects by simple causes. It was this belief that led him to doubt the particle theory of light, with its imponderable ether and its multiple fluids. However, it is unlikely that Fresnel was familiar with the earlier light-wave theories authored by Christiaan Huygens and Leonhard Euler (1707-1783), so he was forced to start from scratch.

Fresnel's initial experiments dealt with the reaction of light when diffracted and led to his discovery of light as a transverse wave, rather than a longitudinal wave as theorized by Huygens in the seventeenth century. The transverse wave theory was validated by Danish astronomer Thomas Bartholin's (1616-1680) experiments, in which it was shown that two rays of light emerging from a piece of Iceland spar differed in properties--a discovery that was completely inconsistent with either particle or longitudinal theories. Fresnel furthered these experiments, advancing many of the first hypotheses dealing with polarized light.

Fresnel's increasing notoriety once again attracted the attention of the government, which, hoping to direct his talents toward more profitable ends, transferred him to the Lighthouse Commission in 1824. This new appointment put great demands upon his time and energy. Though he worked to develop a new echelon lens for lighthouses, his research in light theory dwindled. Added to this new pressure was his losing battle with tuberculosis, an affliction that had plagued him throughout his career and ultimately ended his life.

Many consider Fresnel's work the first major challenge to the theories of particles and imponderables, and his findings a basis for the development of nineteenth-century energetics. Just a half year before his death, he was awarded the Rumford Medal from the Royal Society.