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Righi, Augusto

RIGHI, AUGUSTO

(b. Bologna. Italy, 27 August 1850; d. Bologna, 8 June l920)

physics.

Righi studied in Bologna at the Technical School (1861–1867), then took the four-year mathematics at the University, and after another year graduated from the School of Engineering in 1872, with a dissertation in physics; the previous year he had been appointed assistant to the chair of physics. From 1873 to 1880 he was the physics teacher at the Technical School, and in November 1880 he won the competition for the newly established chair of experimental physics at the University of Palermo. He was professor of physics at the University of Padua from November 1885 to 1889, when he returned to Bologna as professor at the Institute of Physics of the University, He taught there until his death.

Righi is remembered for his studies on electric oscillations, which contributed to wireless telegraphy; his early studies, of greater importance to basic and applied research, are almost forgotten. His graduation thesis (1872) concerned the invention of an induction electrometer that permitted him to investigate weak electrostatic phenomena, including the Volta effect. The device could not only amplify and measure an initially minute electric charge, but also served as an induction electrostatic generator and thus constituted a precise, small-scale model of the van de Graaff accelerator (1933). Righi’s interest in the development of experimental devices as well as the mathematical approach to the interpretation of data led to an important analytical paper on the composition of vibrational motion (1873).’ described by Lissajous some months before. In it he presented original ideas on the composition of two harmonic orthogonal motions (not necessarily of the same period) in a plane, and the resulting curves. Righi also considered the same problem in three dimensions and defined the trajectories that result from three harmonic motions orthogonal to each other. In a subsequent work (1875), taking as his point of departure Helmholtz’ studies in physiological optics, he described the polystereoscope. of his own invention, and proposed a new theorem of projective geometry in order to offer a physical and mathematical solution of the problems of binocular vision and the stereoscopic effect.

At the Technical School of Bologna, Righi turned increasingly to applied research. In 1880 he discovered and described magnetic hysteresis, a few months before Warburg, who is credited with the discovery. Although he patented a microphone using conductive powder and a loudspeaker, his inventions elicited little interest.

Righi’s work at Palermo centered on the Hall and Kerr effects. He discovered that the Hall effect is several thousand times greater in bismuth than in gold and that the magnetic field in bismuth also causes a variation of electric and—as S.-A. Leduc also discovered—thermal resistance. Continuing his research in Padua, Righi also began studying the photoelectric effect, inspired by Hertz’s casual observation (1887) that light that is rich in high-frequency radiation is conducive to a discharge between two electrodes. In a preliminary note of March 1888, Righi demonstrated that when two electrodes are exposed to radiation, rich in ultraviolet rays, they act like a voltaic couple, and he called this phenomenon the photoelectric effect. He also described the connection on series of multiple couples forming a photoelectric battery, pointing out that the maximum effect is obtained with selenium. Wilhelm Hallwachs had published a memoir on this subject less than two months earlier and is credited with priority of discovery, although he had not clarified the phenomenon so completely.

In his lectures at Bologna from 1892 on, Righi demonstrated Hertz’s recent experiments on electromagnetic waves, and in 1893 he divulged his own preliminary findings on their nature. Unlike Marconi, who was attempting to apply Hertzian waves in wireless telegraphy, Righi wished to use them to prove the laws of classical optics. In order not to resort to mirrors, prisms, and lenses of prohibitive dimensions, he reduced the wavelength used in his experiments to only 26 mm (May 1894), thereby opening the new field of microwaves to subsequent research and technology. In this way, Righi had demonstrated that Hertzian waves not only interfere with each other and are refracted and reflected, but that they are also subject to diffraction, absorption, and double refraction, like the waves of the visible spectrum. The results of his experiments were published in the widely read L’ottica delle oscillazioni elettriche (1897), which is still considered a classic of experimental electromagnetism.

Righi reached the zenith of his activity toward the turn of the twentieth century, with important contributions to the study of X rays and of the Zeeman effect. In 1901 he demonstrated that the solution of Maxwell’s equations can be reduced to the solution of one equation with only one vector (in two modes). The following year he described the production of nonlinear relaxation oscillations and discussed their theory. With B. Dessau he wrote the first work on wireless telegraphy, La telegrafia senza fila (1903). In the meantime, he had begun experiments on the conduction of gases under various conditions of pressure and ionization, inside tubes with several electrodes, and under the influence of magnetic fields. He continued these experiments until his death.

From 1918 Righi concentrated on the Michelson-Morley experiment, criticizing it and suggesting modifications. He was fascinated by the theory of relativity, even though he thought it had still not been demonstrated definitely in an experimental way.

BIBLIOGRAPHY

I. Original Works. Righi was a prolific writer; more than 130 papers written before 1900 are listed in the Royal Society Catalogue of Scientific Papers, VIII, 751; XI, 181–182; XII, 619; and XVIII, 206–208. See also Poggendorff, III, 1123–1124; IV, 1251–1253; V, 1052–1053; and VI, 2179–2180. His books include L’ottica delle oscillazioni elettriche (Bologna, 1897), trans. into German by B. Dessau as Die Optik der elektrischen Schwingungen (Leipzig, 1898); La telegrafia senza fila (Bologna, 1903), written with B. Dessau, also in German trans. as Die Telegraphie ohne Draht (Brunswick, 1903, 1907); Modern Theory of Physical Phenomena, Radioactivity, Ions, Electrons, A. Trowbridge, trans. (New York-London, 1904); Sur quelques expériences connues considerées au point de vue de la théorie des électrons (Paris, 1906); and I fenomeni elettro-atomici sotto l’azione del magnetismo (Bologna, 1918), with bibliography of Righi’s writings.

II. Secondary Literature. On Righi and his work, see (listed chronologically) Le feste giubilari di Augusto Righi, per l’inaugurazione del nuovo Istituto di fisica (Bologna, 1907); B. Dessau, L’opera scientifica di Augusto Righi (Rome, 1907), repr. in Giornale di fisica, 11 (1970), 53–73, with intro. by G. Tabarroni; Arduo (July 1920)—an entire issue devoted to Righi; L. Amaduzzi, “Augusto Righi, necrologia,” in Archiginnasio, 15 (1920), 222–226; O. M. Corbino, Commemorazione di Augusto Righi (Rome, 1920); L. Amaduzzi, “Commemorazione di A. Righi,” in Elettrotecnica, 8 (1921), 62–68; P. Cardani, “In memoria di Augusto Righi,” in Nuovo cimento, 6th ser., 21 (1921), 53–186, with bibliography; L. Donati, Commemorazione di Augusto Righi (Bologna, 1923); G. Diaz de Santillani, “Righi,” in Enciclopedia italiana, XXIX, 328–329; L. Imperatori, Augusto Righi (Milan, 1940); P. Veronesi, “Augusto Righi, scienziato,” in Emilia, 1 (1950), 310–311; G. C. Dalla Noce and G. Valle, Scelta di scritti di Augusto Righi (Bologna, 1950), with complete bibliography; G. Valle, “Discorso commemorativo di Augusto Righi,” in Elettrotecnica, 37 (1950), 483–487; G. Tabarroni, Bologna e la storia della radiazione (Bologna, 1965); and “La formazione di Augusto Righi nella Bologna di un secolo fa,” in Strenna storica bolognese, 19 (1969), 271–292; A. M. Angelini, “Rievocazione di Augusto Righi,” in Elettrotecnica, 58 (1971), 57–75; and D. Graffi, “Net 50° anniversario della morte di A. Righi,” in Atti dell’Acca demia delle scienze dell’ Instituto di Bologna. Rendiconti, 12th ser., 8 (1971), 34–42.

Giorgio Tabarroni

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