On This Day
that the addition of sinusoidal functions of the same frequency but different phases is analogous to the addition of forces with different directions,
restates Malus’s law in terms of amplitudes instead of intensities, and
reports that optical rotation can be imitated by “depolarizing” the light with a Fresnel rhomb (in the form of “coupled prisms”), then passing it through an ordinary birefringent lamina, then repolarizing it with a second Fresnel rhomb at 90° to the first.
Augustin-Jean Fresnel (/freɪˈnɛl/, fray-NEL; French: [ɔ.ɡy.stɛ̃ ʒɑ̃ fʁɛ.nɛl]; 10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton’s corpuscular theory, from the late 1830s[1] until the end of the 19th century.
But he is perhaps better known for inventing the catadioptric (reflective/refractive) Fresnel lens and for pioneering the use of “stepped” lenses to extend the visibility of lighthouses, saving unknown numbers of lives at sea. The simpler dioptric (purely refractive) stepped lens, first proposed by Count Buffon [2] and independently reinvented by Fresnel, is used in screen magnifiers and in condenser lenses for overhead projectors.
By expressing Huygens’ principle of secondary waves and Young’s principle of interference in quantitative terms, and supposing that simple colors consist of sinusoidal waves, Fresnel gave the first satisfactory explanation of diffraction by straight edges, including the first satisfactory wave-based explanation of rectilinear propagation.[3] Part of his argument was a proof that the addition of sinusoidal functions of the same frequency but different phases is analogous to the addition of forces with different directions. By further supposing that light waves are purely transverse, Fresnel explained the nature of polarization and lack thereof, the mechanism of chromatic polarization (the colors produced when polarized light is passed through a slice of doubly-refractive crystal followed by a second polarizer), and the transmission and reflection coefficients at a boundary between transparent isotropic media (including Brewster’s angle). Then, by generalizing the direction-speed-polarization relation for calcite, he accounted for the directions and polarizations of the refracted rays in doubly-refractive crystals of the biaxial class (those for which Huygens’ secondary wavefronts are not axisymmetric). The period between the first publication of his pure-transverse-wave hypothesis and the submission of his first correct solution to the biaxial problem was less than a year. Later, he coined the terms linear polarization, circular polarization, and elliptical polarization, explained how optical rotation could be understood as a difference in propagation speeds for the two directions of circular polarization, and (by allowing the reflection coefficient to be complex) accounted for the change in polarization due to total internal reflection, as exploited in the Fresnel rhomb. Defenders of the established corpuscular theory could not match his quantitative explanations of so many phenomena on so few assumptions.
Fresnel’s legacy is the more remarkable in view of his lifelong battle with tuberculosis, to which he succumbed at the age of 39.
Although he did not become a public celebrity in his short lifetime, Fresnel lived just long enough to receive due recognition from his peers, including (on his deathbed) the Rumford Medal of the Royal Society of London, and his name is ubiquitous in the modern terminology of optics and waves. Inevitably, after the wave theory of light was subsumed by Maxwell’s electromagnetic theory in the 1860s, some attention was diverted from the magnitude of Fresnel’s contribution. In the period between Fresnel’s unification of physical optics and Maxwell’s wider unification, a contemporary authority, Professor 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.” [4]
Born On This Day
1871 – Dame Gruev, Bulgarian educator and activist, co-founded the Internal Macedonian Revolutionary Organization (d. 1906)
Damyan Yovanov Gruev or Damjan Jovanov Gruev, often known by his short name Dame Gruev,[1] (January 19, 1871 – December 10, 1906) was а Bulgarian revolutionary and insurgent leader in Ottoman Macedonia and Thrace.[2][3][4][5][6][7][8][9][10][11][12] He was among the founders of the Internal Macedonian Revolutionary Organization (initially known as the Bulgarian Macedonian-Adrianopolitan Revolutionary Committee).[13] Scholars in the Republic of Macedonia consider Gruev to be an ethnic Macedonian revolutionary.[14]
Biography
Early years
Dame Gruev was born in 1871 in the village of Smilevo, (present-day, Republic of Macedonia). He received his elementary education in Smilevo and continued his education in the Bulgarian Men’s High School of Thessaloniki. He was part of a group excluded from the school following a student revolt. In early 1888, the group, consisting of 19 people, including other future IMRO-revolutionaries was attracted by Serbian propaganda. As result they went to study in a Serbian Gymnazium in Belgrade at the expense of the Saint Sava society. Gruev later continued his education in the Grandes écoles in Belgrade. Following yet another revolt, Gruev and his associates were excluded from the Great School and emigrated en bloc to Bulgaria. Gruev was enrolled in Sofia University and, later, in the Young Macedonian Literary Society. He found also the circle “Druzhba”, whose aim was to implement “Article 23” of the Treaty of Berlin (1878) on authonomy of Macedonia. In 1891 Gruev was expelled from the University as he was suspected in the assassination of the Minister Hristo Belchev, but subsequently this allegation turned out to be groundless.
Next, Gruev left the University and returned to Ottoman Macedonia region to apply himself to a new revolutionary organization. In order to carry out his plans more successfully, and possibly to avert the suspicion of the Turkish authorities, he decided to become a Bulgarian school teacher. The first two years after his return to Macedonia region he spent teaching, first in his native village of Smilevo, and later in the town of Prilep. Later, Gruev established himself in Thessaloniki and here laid the foundation of BMARC (the Bulgarian Macedonian-Adrianople Revolutionary Committees). With the cooperation of Hristo Tatarchev and Petar Pop Arsov among others, he came up with the Constitution and By-laws of IMARC. It was to be a secret organization under the guidance of a Central Committee, with local revolutionary committees throughout Macedonia and the region of Adrianople (Edirne). These regions were to be divided into revolutionary districts or rayons like in the April Uprising. In accordance with the Constitution, the first Central Revolutionary Committee was formed in the summer of 1894, under the chairmanship of Hristo Tatarchev.
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A new survey of more than 19,000 U.S. adults sheds some light on why public trust in the news media is at an all-time low. The key takeaway is that Americans think the news media is an important part of our democracy, but they don’t think the media is fulfilling that role. The survey is part of the Knight Foundation Trust, Media and Democracy initiative, and is one of the largest on this topic. It as done by the Gallup Organization. (Click here to read the whole report.)
On Jan. 23, The Washington Post will broadcast live a series of panels exploring the implications of the survey, featuring Judy Woodruff of PBS and Bret Baier of Fox News. You can tune in at PostLive from 9:30 to 11 a.m. ET. Ten findings that stood out from the survey:
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- Wikimedia Commons picture of the day for June 10 June 10, 2026Picture of the day Hills of České Středohoří (Central Bohemian Highlands): Malý Křižák, Křižák, Brník, Srdov, Milá
- Wikimedia Commons picture of the day for June 9 June 9, 2026Picture of the day Ringed kingfisher flying with freshly caught fish in Mato Grosso, Brazil
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