....Optics Highlights

VI. Wave Optics

The shift to the wave explanation began at the beginning of the 19th century. In 1801 Thomas Young discovered the interference of light from adjacent pinholes and established the wave theory of light. Ridiculed in England, Young’s theory was championed in France by Fresnel and Arago who faced the opposition of senior scientists, such as Laplace, Fourier and Poisson, who supported the corpuscular theory. The polarization of light by reflection had been discovered in 1808 by Malus and the polarizing angle discovered by Brewster in 1811. Fresnel was able to explain polarization using Young’s suggestion that light was a transverse vibration and his analyses of diffraction effects were convincing, but the final proof of the wave theory depended on the experimental proof that light traveled more slowly in denser media, since the corpuscular theory required the reverse. Arago, and then Foucault and Fizeau (who rediscovered the Doppler effect), attempted to measure the relative velocities in air and water. It was not until 1849 that the measurement was finally achieved. In the latter half of the 19th Century, the unsuccessful attempts of Fizeau and then of Michelson and Morley to measure the drag of the ether on light waves led to Einstein’s Theory of Relativity in 1905.
 
  Thomas Young (1773-1829), as his epitaph in Westminster Abbey states, was "a man alike eminent in almost every department of human learning." As a medical student he discovered the way the eye lens changes shape in order to focus and the cause of astigmatism. Proficient in many languages, he later made the first nearly correct translation of the Rosetta Stone. His diverse scientific accomplishments included contributions to the theory of elasticity. Influenced by Euler’s arguments, he attempted to prove the wave nature of light, discovered interference and published numerous papers arguing in favor of the wave theory during the first decade of the 19th century. A savage anonymous review of his work in 1803 in the Edinburgh Review (now known to have been due to Lord Brougham, a proponent of the corpuscular theory) cast Young into scientific limbo for ten years.
Augustin-Jean Fresnel (1788-1827) was educated at the École Polytechnique as a civil engineer and served in the roads and bridges corps. He lost his engineering post and was jailed briefly for opposing Napoleon's return from Elba in 1815. He began to privately pursue experiments in optics. Constructing simple experimental apparatus with the aid of the village blacksmith, he rediscovered interference and provided a mathematical theory of diffraction based on the wave theory. In contrast to the work being done in England, Fresnel relied on mathematical analysis which enabled him to make predictions which could be accurately verified and he removed many of the objections to the wave theory of light. Poisson who was on the review committee of the Paris Académie in 1819 objected that the theory predicted a bright spot in the center of the shadow of a circular disk. Arago was asked to perform the experiment; when the phenomenon was observed, Fresnel’s paper won the prize offered for a memoir on diffraction.
François Arago (1786-1853), like Fresnel, was educated at the École Polytechnique, where at age 23 he became professor of analytic geometry. He was active in French politics, became director of the Paris Observatory, permanent secretary of the French Academy of Sciences, and was minister of war and marine in the government formed after the 1848 revolution. In 1838, he proposed the experiment to compare the velocity of light in air and in water. However, by the time the experiment was ready in 1850, he had lost his sight and it remained for Fizeau and Foucalt to carry out the work. Arago played a rather dubious role in the history of photography: he championed the system of his friend, Daguerre, and apparently used his influence to persuade Hippolyte Bayard, another inventor who actually exhibited earlier than Daguerre, to keep his process secret so that the French Academy bought the rights to Daguerre’s invention.
Etienne-Louis Malus (1775-1812) was another graduate of the École Polytechnique. He rose to the rank of colonel in Napoleon’s corps of engineers, fought in Egypt, and contracted the plague during Napoleon’s aborted campaign in Palestine. Posted to Europe after 1801, he began research in optics. In a famous incident, he discovered polarization by reflection while toying with a calcite crystal and looking out from his apartment towards the windows of the Luxembourg palace. Malus and Laplace explained the effect through a theory of short range forces of matter on light corpuscles.
(Sir) David Brewster (1781-1868) was a Church of Scotland minister who abandoned the ministry in favor of science and invention. He contributed important experimental investigations of polarization, reflection and absorption and obtained more than a hundred patents, but the profits from his most famous invention, the kaleidoscope, were denied him due to a faulty patent application. From 1838 on he was principal, first at a college of St. Andrews, and then at the University of Edinburgh. It was said of him that "nobody ever had dealings with him and escaped a quarrel." He became one of the last and most contentious opponents of the wave theory of light, leading the final struggles in the 1850's. When one his papers was rejected by the Royal Society, he complained that it was because of anti-Scottish English prejudice.
Jean-Bernard-Leon Foucault (1819-1869) and his long-term co-worker, Fizeau, were contemporaries who were trained as physicians and became self-taught physicists who worked together in photography. At first they also cooperated to carry out the speed of light measurement suggested by Arago. Foucalt’s paper appeared in 1850, the year following Fizeau’s publication on the velocities of light in air and water. In 1851, he demonstrated the rotation of the earth with a pendulum on a swivel support hung in the Pantheon in Paris. (Until a few years ago, a similar pendulum swung here in the domed lobby of our mathematics building at the University of Maryland.)
Armand-Hippolyte-Louis Fizeau (1819-1896) was independently wealthy and was able to finance his experiments himself. His determination of the speed of light was the first terrestrial measurement. He invented one of the first interferometers and in 1851 used it in the first attempt to measure the effect of the earth’s velocity on the speed of light and demonstrate the existence of the ether.
Johann Christian Doppler (1803 - 1853) was an Austrian physicist who published a paper in 1842 "Concerning the Colored Light of Double Stars" which first described how the frequency of light and sound is changed by the relative velocity of the source and observer. His paper seems to have gone unnoticed, and the effect was "rediscovered" by Fizeau in 1848. In 1850 Doppler was made director of the Physical Institute and professor of physics at the University of Vienna.
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