Étienne-Louis Malus (; ; 23 July 1775 – 23 February 1812) was a French

officer An officer is a person who has a position of authority in a hierarchical organization. The term derives from Old French ''oficier'' "officer, official" (early 14c., Modern French ''officier''), from Medieval Latin ''officiarius'' "an officer," fro ...

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, and

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. Malus was born in

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and studied at the military engineering school at Mezires where he was taught by

Gaspard Monge Gaspard Monge, Comte de Péluse (; 9 May 1746 – 28 July 1818) was a French mathematician, commonly presented as the inventor of descriptive geometry, (the mathematical basis of) technical drawing, and the father of differential geometry. Dur ...

.University of St Andrews website, ''Étienne-Louis Malus''
/ref> Cambridge University Press website, ''Pioneers in Optics: Leonhard Euler and Étienne-Louis Malus'', article by Michael W. Davidson
/ref> He participated in Napoleon's expedition into Egypt (1798 to 1801). Britannica website, ''Étienne-Louis Malus''
/ref> He was also a member of the mathematics section of the Institut d'Égypte. Malus became a member of the

Académie des Sciences The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...

in 1810. In 1810 the

Royal Society of London The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, r ...

awarded him the Rumford Medal. His mathematical work was almost entirely concerned with the study of

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

. He studied

geometric Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...

systems called ''ray systems'', closely connected to

Julius Plücker Julius Plücker (16 June 1801 – 22 May 1868) was a German mathematician and physicist. He made fundamental contributions to the field of analytical geometry and was a pioneer in the investigations of cathode rays that led eventually to the di ...

's '' line geometry''. He conducted experiments to verify

Christiaan Huygens Christiaan Huygens, Halen, Lord of Zeelhem, ( , ; ; also spelled Huyghens; ; 14 April 1629 – 8 July 1695) was a Dutch mathematician, physicist, engineer, astronomer, and inventor who is regarded as a key figure in the Scientific Revolution ...

's theories of light and rewrote the theory in analytical form. His discovery of the polarization of light by reflection was published in 1809 and his theory of double refraction of light in

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s, in 1810. Malus attempted to identify the relationship between the polarising angle of reflection that he had discovered, and the

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

of the reflecting material. While he deduced the correct relation for

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, he was unable to do so for glasses due to the low quality of materials available to him (the refractive index of most glasses available at that time varied between the surface and the interior of the glass). It was not until 1815 that Sir David Brewster was able to experiment with higher quality glasses and correctly formulate what is known as Brewster's law. This law was later explained theoretically by Augustin Fresnel, as a special case of his

Fresnel equations The Fresnel equations (or Fresnel coefficients) describe the reflection and transmission of light (or electromagnetic radiation in general) when incident on an interface between different optical media. They were deduced by French engineer and ...

. Malus is probably best remembered for Malus's law, giving the resultant intensity, when a polariser is placed in the path of an incident beam. A follower of

Laplace Pierre-Simon, Marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French polymath, a scholar whose work has been instrumental in the fields of physics, astronomy, mathematics, engineering, statistics, and philosophy. He summariz ...

, both his statement of the Malus's law and his earlier works on polarisation and

birefringence Birefringence, also called double refraction, is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are described as birefrin ...

were formulated using the corpuscular theory of light. His name is one of the 72 names inscribed on the Eiffel tower.

"Discovery" of polarization

In 1810, Malus, while engaged on the theory of double refraction, casually examined through a doubly refracting prism of quartz the sunlight reflected from the windows of the

Luxembourg palace The Luxembourg Palace (, ) is at 15 Rue de Vaugirard in the 6th arrondissement of Paris, France. It was originally built (1615–1645) to the designs of the French architect Salomon de Brosse to be the royal residence of the regent Marie de' Med ...

. He was surprised to find that the two rays alternately disappeared as the prism was rotated through successive right angles, in other words, that the reflected light had acquired properties exactly corresponding to those of the rays transmitted through Iceland spar. He named this phenomenon polarization, and thought it could not be explained by wave theory of light. Instead, he explained it by stating that light- corpuscules have polarity (like magnetic poles).

Selected works

''Mémoire sur la mesure du pouvoir réfringent des corps opaques''
in Nouveau bulletin des sciences de la Société philomathique de Paris, 1 (1807), 77–81
''Mémoire sur de nouveaux phénomènes d’optique''
ibid., 2 (1811), 291–295 * ''Traité d’optique''. in Mémoires présentés à l’Institut des sciences par divers savants, 2 (1811), 214–302 * ''Théorie de la double réfraction de la lumière dans les substances cristallines''. ibid., 303–508

Work

Malus mathematically analyzed the properties of a system of continuous light rays in three dimensions. He found the equation of caustic surfaces and the Malus theorem: Rays of light that are emitted from a point source, after which they have been reflected on a surface, are all normal to a common surface, but after the second refraction they no longer have this property. If the perpendicular surface is identified with a wave front, it is obvious that this result is false, which Malus did not realize because he adhered to Newton's theory of light emission. Malus's theorem was not proved until 1824 by W. R. Hamilton, with

Adolphe Quetelet Lambert Adolphe Jacques Quetelet FRSF or FRSE (; 22 February 1796 – 17 February 1874) was a Belgian- French astronomer, mathematician, statistician and sociologist who founded and directed the Brussels Observatory and was influential ...

and Joseph Diez Gergonne giving a separate proof in 1825. Hal Science website, ''A direct proof of Malus’ theorem using the symplectic structure of the set of oriented straight lines''’, by Charle-Michel Marle. 2014. hal-01059542 (page 4)
/ref>

References

External links

*
English translation of his paper "Optique"
{{DEFAULTSORT:Malus, Etienne-Louis 1775 births 1812 deaths École Polytechnique alumni French mathematicians French physicists Members of the French Academy of Sciences Burials at Père Lachaise Cemetery

"Discovery" of polarization

Selected works

Work

See also

References

External links