Augustin-Jean Fresnel

Lore & Background

Fresnel was born in Broglie, Normandy, the second of four sons of architect Jacques Fresnel and Augustine Mérimée. The family moved to Cherbourg and later to Mathieu. Augustin was initially home-schooled by his mother and considered slow, though a story that he hardly read until age eight is disputed. At age nine or ten he was known for making toy bows and guns. In 1801 he was sent to the École Centrale at Caen, and in late 1804 he entered the École Polytechnique, placing 17th in the entrance exam. There he excelled in drawing and geometry, winning a prize for solving a geometry problem posed by Adrien-Marie Legendre. He graduated in 1806 and then enrolled at the École Nationale des Ponts et Chaussées, graduating in 1809 and entering the Corps des Ponts et Chaussées as an engineer in training.

Fresnel's parents were Roman Catholics of the Jansenist sect, and religion was central to his upbringing. He remained a Jansenist, viewing his talents as gifts from God and duty-bound to use them for others. He never gained a permanent academic teaching post, possibly due to his Jansenism; his only teaching appointment was at the Athénée in the winter of 1819–20. He had a lifelong battle with tuberculosis, to which he succumbed at age 39. On his deathbed he received the Rumford Medal of the Royal Society.

His engineering assignments included a posting to Vendée in 1811, where he anticipated the Solvay process for soda ash, and later to Nyons in Drôme to assist with an imperial highway. In 1815, during Napoleon's return from Elba, Fresnel left his post to join the royalist resistance, was suspended, and spent his enforced leisure at his mother's house in Mathieu beginning his optical experiments. In 1819 he was seconded to the Commission des Phares to improve lighthouse illumination, leading to his recommendation of stepped lenses.

Reader's Guide

Fresnel's significance lies in his transformation of physical optics. His work on diffraction (1815–1818) provided the first satisfactory wave-based explanation of rectilinear propagation and colored fringes. By proposing that light waves are purely transverse, he explained polarization and later worked on double refraction. His wave theory fully supplanted Newton's corpuscular theory from the late 1830s until the end of the 19th century. After Maxwell's electromagnetic theory subsumed the wave theory in the 1860s, some attention diverted from Fresnel's contribution, but contemporary authority Humphrey Lloyd described Fresnel's transverse-wave theory as 'the noblest fabric which has ever adorned the domain of physical science, Newton's system of the universe alone excepted.' His practical legacy includes the catadioptric Fresnel lens and stepped lenses for lighthouses, which saved countless lives at sea. The simpler dioptric stepped lens, first proposed by Count Buffon and independently reinvented by Fresnel, is used in screen magnifiers and condenser lenses. His name remains ubiquitous in modern optics and wave terminology.

Did You Know?

• Fresnel anticipated the Solvay process for producing soda ash in 1811, though recycling of ammonia was not considered.
• He was placed on suspension during the Hundred Days for leaving his post to join the royalist resistance against Napoleon.
• His brother Léonor succeeded him as secretary of the Lighthouse Commission and helped edit his collected works.
• Fresnel's only teaching appointment was at the Athénée in the winter of 1819–20.

Notable Quotes (Wikiquote)

"Je ne trouve rien de si pénible que d'avoir à mener des hommes." — Augustin-Jean Fresnel "I find nothing so painful as having to lead men." — Augustin-Jean Fresnel "Ce n'est point l'observation mais la théorie qui m'a conduit à ce résultat que l'expérience a ensuite confirmé." — Augustin-Jean Fresnel "It's not observation but theory that led me to this result that experience has confirmed afterwards." — Augustin-Jean Fresnel