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Armand Hippolyte Louis Fizeau (French: [ipɔlit fizo]; 23 September 1819 – 18 September 1896) was a French physicist who, in 1849, measured the speed of light to within 5% accuracy. In 1851, he measured the speed of light in moving water in an experiment known as the Fizeau experiment .
In 1848–49, Hippolyte Fizeau determined the speed of light using an intense light source at the bell tower of his father's holiday home in Suresnes, and a mirror 8,633 meters away on Montmartre. [2] The light source was interrupted by a rotating cogwheel with 720 notches that could be rotated at a variable speed several times a second.
Figure 1. Apparatus used in the Fizeau experiment. The Fizeau experiment was carried out by Hippolyte Fizeau in 1851 to measure the relative speeds of light in moving water. . Fizeau used a special interferometer arrangement to measure the effect of movement of a medium upon the speed of lig
In 1845, Arago suggested to Fizeau and Foucault that they attempt to measure the speed of light. Sometime in 1849, however, it appears that the two had a falling out, and they parted ways. [5]: 124 [3] In 1848−49, Fizeau used, not a rotating mirror, but a toothed wheel apparatus to perform an absolute measurement of the speed of light in air.
In 1851, Fizeau used an entirely different form of interferometer to measure the effect of movement of a medium upon the speed of light, as seen in Fig. 3. According to the theories prevailing at the time, light traveling through a moving medium would be dragged along by the medium, so the measured speed of the light would be a simple sum of ...
In classical physics, light is ... This is the working principle behind experiments by Hippolyte ... They used it in 1972 to measure the speed of light in ...
Depending on the value assumed for the astronomical unit, this yields the speed of light as just a little more than 300,000 kilometres per second. The first measurements of the speed of light using completely terrestrial apparatus were published in 1849 by Hippolyte Fizeau (1819–96). Compared to values accepted today, Fizeau's result (about ...
1845 – Michael Faraday discovers that light propagation in a material can be influenced by external magnetic fields (Faraday effect) 1849 – Hippolyte Fizeau and Jean-Bernard Foucault measure the speed of light to be about 298,000 km/s