Augustin-Jean Fresnel was a nineteenth century French physicist, most often remembered for the invention of unique compound lenses designed to produce parallel beams of light, which are still used widely in lighthouses. Born in Broglie, France on May 10, 1788, Fresnel was the son of an architect and received a strict, religious upbringing. His parents were Jansenists, a sect of Roman Catholics that believed only a small, predestined group would receive salvation and that the multitudes could not change their fate through their actions on Earth. Fresnel's early education was provided by his parents and he was considered a slow learner, barely able to read by the age of 8. When he was 12-years-old, however, Fresnel began formal studies at the Central School in Caen, where he was introduced to the wonders of science and demonstrated an aptitude in mathematics.
Fresnel's academic predilections inspired him to pursue a career in engineering. He entered the Polytechnic School in Paris in 1804 and, two years later, the School of Civil Engineering. Following graduation, he worked on engineering projects for several years in a variety of French government departments, but temporarily lost his post when Napoleon returned from Elba in 1815. Having already begun performing scientific work in his spare time, the change of events provided Fresnel with the opportunity to increase his efforts in this arena, and he soon began to focus on optics. Even when he was provided with a new engineering position in Paris after the second restoration, Fresnel continued his scientific investigations.
In the field of optics, Fresnel derived formulas to explain reflection, refraction, double refraction, and the polarization of light reflected from a transparent substance. Fresnel also developed a wave theory of diffraction. He created various devices to produce interference fringes in order to demonstrate the interference of light wavelets. Using his inventions, Fresnel was the first to prove that the wave motion of light is transverse. He accomplished this task by polarizing light beams in different planes and showing that the two beams do not exhibit interference effects.
In 1822, Fresnel invented the lens that is now used in lighthouses around the world. The Fresnel lens appears much like a giant glass beehive with a lamp in the center. The lens is composed of rings of glass prisms positioned above and below the lamp to bend and concentrate the light into a bright beam. The Fresnel lighthouse lens works so well that the light can be seen from a distance of 20 or more miles. Before Fresnel's invention, lighthouses used mirrors to reflect light, and could be seen only at short distances and hardly at all during foggy or stormy days. Lighthouses equipped with Fresnel's lenses have helped save many ships from going aground or crashing into rocky coasts.
Although he received little public recognition for his efforts during his lifetime, Fresnel was bestowed with various honors by his fellow scientists. He was elected a member of the French Academy of Sciences in 1823 and became a member of the Royal Society of London two years later. The British organization awarded him with the prestigious Rumford Medal in what was to be the final year of his life. Having struggled with ill health since his early childhood, Fresnel died of consumption at Ville-d'Avray, France on July 14, 1827.
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