Biography

 

Possessed of a gift for invention from early childhood, Fresnel very quickly proved sufficiently gifted in mathematics to join Polytechnique in 1804 at the age of sixteen and a half and Ecole des ponts two years later.

In his first positions in Vendée and in the Drôme, he tackled a huge range of subjects:annual stellar aberration, probe manufacture, hydraulic elevator, the expansion of gases.Then, in 1814, he began to look at the properties of light.He began to study diffraction and lightwave interferences and the wave aspects of light.In 1815, he published essays backing his theory that light is caused by vibrations propagated in an elastic medium called aether.Also at this time, he completed the two-mirror experiment – which bears his name – proving the existence of interferences, which is the true experimental basis for wave theory.In 1816, he entered the Grand Prix in mathematical sciences launched by the Academy of Sciences on “the diffraction of direct and reflected rays of light”. With the support of François Arago and André Ampère, and after heated discussions, because Fresnel’s essay questioned the theories of Newton and Huygens, the Academy of Sciences awarded him the prize in 1819. His essay shows that the fringes produced by an opaque body depend only on the shape of that obstacle and not on the nature of its constituent substance.After this, he turned to the study of polarised ray interferences and reached the conclusion that the vibrations of the light are a transverse wave.He also discovered circular polarisation, conducted more detailed research on the phenomenon of dual diffraction and established laws for the propagation of light in crystalline media.Finally, he formulated the theory of the reflection and refraction of polarised light.Amidst his theoretical research, Augustin Fresnel continued to invent, and from 1819 did revolutionary work on lighthouse technology:he replaced the mirror projection system by he compound lens system, and with Arago’s help, he designed a lens with several concentric annular sections and a double air supply, which increased the power of lighthouse beams.After successful tests conducted on the Arc de Triomphe, his lens system was installed in the Cordouan lighthouse in 1823. Whereas the parabolic projectors previously used had a maximum range of 20 km, the Fresnel system’s range was more than 60 km.He went on to perfect the technique, with the result that 19th century France became a model for lighthouse production around the world.

He made his brother Léonor his successor at the Lighthouse service before his death in 1827 at the age of 39, a recipient of the Rumford Medal from the Royal Society of London.

 

 

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