Jean-Baptiste Biot (21.04.1774-3.02.1862) was a French physicist and a member of the Paris Academy of Sciences (1803). He was born in Paris. He graduated from the École Polytechnique (1797). From 1800 he was professor at the Collège de France and in 1808-49 at the University of Paris.
His work concerned optics, electromagnetism, acoustics and the history of science. He determined the speed of sound in solids (1809, 1823). In 1811 he discovered polarisation on refraction (independently of É. Malus), and in 1815 circular polarisation (independently of D. Arago and D. Brewster). He studied the polarisation properties of many substances. He detected the optical activity of certain liquids (in turpentine, in particular, in 1815), establishing that they have the ability to rotate the plane of polarisation. He discovered the law of the rotation of the plane of polarisation of light (Biot's law) and established the existence of right- and left-rotating substances (1815). Biot's studies of the rotation of the plane of polarisation of light in crystals and in organic substances began saccharimetry (1836). In 1820, together with F. Savart, he discovered the law that determines the magnetic field strength of a straight current (the Biot–Savart law). Together with Arago he carried out measurements of the density and refractive index of various gases (1806). He rediscovered (1814) the polarisation properties of tourmaline. He was the author of a course of physics widely known in its time. A Fellow of the Royal Society (1815) and of the St Petersburg Academy of Sciences (1819). The B. Rumford Medal (1840)