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Augusto Righi
b. August 27, 1850, Bologna, Italy
d. June 8, 1920, Bologna, Italy
Augusto Righi was an Italian physicist who played an important role in the
development of electromagnetism and, thus, indirectly influenced wireless
telegraphy. Between 1893 and 1896, Righi developed Hertz's work and made it
more exact, using a new type of oscillator, which could generate electromagnetic
waves of a few centimeters. Righi was the first experimenter to obtain double
refraction of electromagnetic waves.
Augusto Righi was born on August 27, 1850, in Bologna, Italy. He received his degree
in engineering at the age of 22 from the Bologna University. He was teaching physics
from 1873 to 1880 at the Bologna Technical Institute, from 1880 to 1885 at the Palermo
University, and from 1885 to 1889 at Padua University and then at the University of
Bologna. Augusto Righi was appointed to the Chair of Physics at the Faculty of
Science, University of Bologna, in 1899. He taught in Bologna for 32 years and
published more than 250 scientific papers.
Among them many related to electricity and electromagnetism (Righi's papers on
line):
- a group of papers on Volta effect (from 1874 to 1887)
- three memories on electric discharge in gases at atmospheric pressure (from 1876 to
1886)
- papers on theories of capacitors and induction machines (1879)
- a memory on magnetisation of steel (1880)
- two memories on electric shadows (1881-82)
- two memories on Kerr effect (starting from 1884)
- nine memories on photoelectric effect (1888-89)
- two memories on electromagnetic and electrodynamic forces (1889-1890)
- a series of memories on electric sparks (1891-92-95)
- a classical textbook of the Electromagnetism entitled "Optics of the electrical
oscillations" (1897)
- a paper on the Zeeman effect (1898)
- two notes on an experimental method for the study of absorption of light in a magnetic
field (1898)
- a paper on wireless telegraphy entitled "The wireless Telegraphy " (1903)
- a paper on the electromagnetic mass of the electron (1906)
- a paper on movement in an electromagnetic field of a system electron-positive ion
(1910)
- a book on "Electro-atomic phenomena in magnetic field" (1918)
Augusto Righi applied his talents to experimental work in electro-magnetic studies and
solid-state physics. He was the first scholar to demonstrate the hysteresis effect of iron
and magnetic materials and his contributions to the study of Hall and Kerr effects
brought to light some basic aspects that were later explained later by electronic theory.
After Hertz announced his discovery of electromagnetic waves, Righi investigated
them, especially their optical properties, and published the results in a treatise, Optice
Elettrica, in 1897. He noticed that the smaller the spheres on the exciters, the shorter the
waves, approaching those of light. Righi propagated electric waves as short as 2.5
centimeters, whereas Hertz had produced them 30 centimeters in length. Righi
improved the Hertz oscillator that generated the waves; he placed the spark gap in
vaseline oil and made the waves more consistent and steady.
Using his 'sphere oscillator' Augusto Righi carried out a series of famous experiments
which proved Maxwell's theories to be correct. This work was of fundamental
importance in the training of the young scientist, Guglielmo Marconi, who carried out
his early research in Righi's laboratory.
Two columns of plastic material upon a black, painted, mahogany base vertically
support the oscillating system through brass screw rings. Unlike Hertz's oscillator,
which used the oscillation of only one electromagnetic discharge in the air, Righi's
oscillator consists of a system with three sparks, and the oscillating discharge does not
take place in the air. The oscillator consists of four metal spheres, which are insulated
from each other: the larger ones, each emerged halfway in paraffin oil, are in the centre
and the smaller ones are at the extremities. By connecting the smaller spheres to the
secondary circuit of a Ruhmkorff coil, the system starts oscillating: the interruption of
the discharge in the paraffin oil electromagnetically induces an attenuated discharge in
the opposite direction. Every opening and closing of the coil's switch, therefore,
generates a new series of dampened oscillations. The oscillations are generated only in
the case of an instantaneous discharge. The surface of the sphere must therefore be
smooth to avoid leakages due to roughness. The immersion into the paraffin oil favours
the production of an instantaneous discharge, a more uniform emission of electricity,
and hampers the deterioration of the surfaces of the spheres caused by the sparks (in the
case of Hertz's oscillator the surface must be frequently cleaned).
Righi's three sparks oscillator, c. 1900
The origin of this instrument is linked directly to the experimental verification of the
electromagnetic theory of light developed by the famous Scottish physicist J.C.
Maxwell (1831-1879). The first experimental verification of this theory was made by
the German physicist Henrich Hertz (1857-1894) who used an oscillator and a resonator
to verify in a series of experiments (1886-1889) that the electric waves reflected,
refracted and interfered just as beams of light do. In his verification Hertz used mirrors,
lenses, and prisms of very encumbering dimensions and also an oscillator with metal
spheres that was able to produce a wave with a minimum length of 66 cm. A more
accurate verification of Maxwell's hypothesis was given only in 1893 by the physicist
Augusto Righi of Bologna due to changes and improvements he had made to the
instruments used. In particular, in order to reduce the wave length produced by Hertz's
oscillator and to reduce the size of the optical apparatus needed to prove the theory, he
made a new oscillator, or a spark gap with three sparks, to reduce the capacity and the
self-induction. The oscillator consisted of two central metal spheres that emerged into a
container filled with paraffin oil, through which the oscillatory discharge was produced.
The idea was not new (Righi himself had mentioned the previous attempts by the
Geneva physicists De la Rive and Sarasin). However, it quickly led the physicist from
Bologna to work with wave lengths of about 10 cm until he produced microwaves that
were 26 mm long and until he proved the complete analogy between the "electric
waves" and the radiations of light and heat.
Augusto Righi contributed a new detector by cutting thin lines on the back of a mirror,
dividing the metallic surface with a diamond point into narrow discontinuous strips.
This provided a spark-distance much finer than could be attained by a micrometer gap,
hence affording greater sensitivity.
But it is said that Righi's work in generation and detection of electric waves was not in
itself as important as the fact that it was partly through him that Marconi found
encouragement. Although Marconi was never enrolled as a student at the University of
Bologna, he did hear Righi lecture. Actually, Augusto Righi and Guglielmo Marconi
had close relations for a long period of time.
During the last years of his life Righi began experiments on the conduction of gases
under various conditions of pressure and ionization in magnetic field. From 1918 he
concentrated on the Michelson-Morley experiment, criticizing it and suggesting
modifications. He was fascinated by the theory of relativity, though he believed that the
theory lacked convincing experimental support. Righi was a member of several national
scientific associations, such as the prestigious Accademia dei Lincei.
Righi died in Bologna on June, 8, 1920.