Editing Augustin-Jean Fresnel (section)

== Legacy ==

[[File:Cordouan6.jpg|thumb|The lantern room of the [[Cordouan Lighthouse]], in which the first Fresnel lens entered service in 1823. The current fixed catadioptric "beehive" lens replaced Fresnel's original rotating lens in 1854.{{r|pharedeC}}]]

Within a century of Fresnel's initial stepped-lens proposal, more than 10,000 lights with Fresnel lenses were protecting lives and property around the world.<ref>Levitt, 2013, p.&nbsp;19.</ref> Concerning the other benefits, the science historian Theresa H. Levitt has remarked:
{{blockquote|Everywhere I looked, the story repeated itself. The moment a Fresnel lens appeared at a location was the moment that region became linked into the world economy.<ref>Levitt, 2013, p.&nbsp;8.</ref>}}

In the history of physical optics, Fresnel's successful revival of the wave theory nominates him as the pivotal figure between Newton, who held that light consisted of corpuscles, and [[James Clerk Maxwell]], who established that light waves are electromagnetic. Whereas [[Albert Einstein]] described Maxwell's work as "the most profound and the most fruitful that physics has experienced since the time of Newton,"{{hsp}}{{r|jamesCMF}} commentators of the era between Fresnel and Maxwell made similarly strong statements about Fresnel:
* MacCullagh, as early as 1830, wrote that Fresnel's mechanical theory of double refraction "would do honour to the sagacity of Newton".{{r|macCullagh-1830|p=78}}
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* Lloyd, in his ''Report on the progress and present state of physical optics'' (1834) for the [[British Science Association|British Association for the Advancement of Science]], surveyed previous knowledge of double refraction and declared:<blockquote>The theory of Fresnel to which I now proceed,—and which not only embraces all the known phenomena, but has even outstripped observation, and predicted consequences which were afterwards fully verified,—will, I am persuaded, be regarded as the finest generalization in physical science which has been made since the discovery of universal gravitation.<ref>Lloyd, 1834, p.&nbsp;382.</ref></blockquote>In 1841, Lloyd published his ''Lectures on the Wave-theory of Light'', in which he 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."{{hsp}}{{r|lloyd-1841}}
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* [[William Whewell]], in all three editions of his ''History of the Inductive Sciences'' (1837, 1847, and 1857), at the end of Book&nbsp;{{serif|IX}}, compared the histories of physical astronomy and physical optics and concluded:<blockquote>It would, perhaps, be too fanciful to attempt to establish a parallelism between the prominent persons who figure in these two histories. If we were to do this, we must consider Huyghens and [[Robert Hooke|Hooke]] as standing in the place of [[Copernicus]], since, like him, they announced the true theory, but left it to a future age to give it development and mechanical confirmation; [[Étienne-Louis Malus|Malus]] and Brewster, grouping them together, correspond to [[Tycho Brahe]] and [[Johannes Kepler|Kepler]], laborious in accumulating observations, inventive and happy in discovering laws of phenomena; and Young and Fresnel combined, make up the Newton of optical science.<ref>Whewell, 1857, pp.&nbsp;370–371.</ref></blockquote>

What Whewell called the "true theory" has since undergone two major revisions. The first, by Maxwell, specified the physical fields whose variations constitute the waves of light. Without the benefit of this knowledge, Fresnel managed to construct the world's first coherent theory of light, showing in retrospect that his methods are applicable to multiple types of waves. The second revision, initiated by Einstein's explanation of the [[photoelectric effect]], supposed that the energy of light waves was divided into [[quantum|quanta]], which were eventually identified with particles called [[photon]]s. But photons did not exactly correspond to Newton's corpuscles; for example, Newton's explanation of ordinary refraction required the corpuscles to travel faster in media of higher refractive index, which photons do not. Neither did photons displace waves; rather, they led to the paradox of [[wave–particle duality]]. Moreover, the phenomena studied by Fresnel, which included nearly all the optical phenomena known at his time, are still most easily explained in terms of the ''wave'' nature of light. So it was that, as late as 1927, the astronomer [[E. M. Antoniadi|Eugène Michel Antoniadi]] declared Fresnel to be "the dominant figure in optics."{{nnbsp}}{{r|antoniadi-1927}}