Question: What  French physicist and mathematician was involved in the invention of radio?
Context: Many people were involved in the invention of radio as we know it today.  Experimental work on the connection between electricity and magnetism began around 1820 with the work of Hans Christian Ørsted, and continued with the work of André-Marie Ampère, Joseph Henry, and Michael Faraday.  These investigations culminated in a theory of electromagnetism developed by James Clerk Maxwell, which predicted the existence of electromagnetic waves. Jules Antoine Lissajous (] ) (March 4, 1822 in Versailles – June 24, 1880 in Plombières-les-Dijon) was a French physicist, after whom Lissajous figures are named.  Among other innovations, Lissajous invented the Lissajous apparatus, a device that creates the figures that bear his name.  In it, a beam of light is bounced off a mirror attached to a vibrating tuning fork, and then reflected off a second mirror attached to a perpendicularly oriented vibrating tuning fork (usually of a different pitch, creating a specific harmonic interval), onto a wall, resulting in a Lissajous figure.  This led to the invention of other apparatus such as the harmonograph. Jean-Pierre Christin (May 31, 1683 – January 19, 1755) was a French physicist, mathematician, astronomer and musician.  His proposal to reverse the Celsius thermometer scale (from water boiling at 0 degrees and ice melting at 100 degrees, to water boiling at 100 degrees and ice melting at 0 degrees) was widely accepted and is still in use today. The coherer is a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the 20th century.  Its use in radio was based on the 1890 findings of French physicist Edouard Branly and adapted by other physicists and inventors over the next ten years.  The device consists of a tube or capsule containing two electrodes spaced a small distance apart with loose metal filings in the space between.  When a radio frequency signal is applied to the device, the metal particles would cling together or "cohere", reducing the initial high resistance of the device, thereby allowing a much greater direct current to flow through it.  In a receiver, the current would activate a bell, or a Morse paper tape recorder to make a record of the received signal.  The metal filings in the coherer remained conductive after the signal (pulse) ended so that the coherer had to be "decohered" by tapping it with a clapper, such as a doorbell ringer, each time a signal was received, thereby restoring the coherer to its original state.  Coherers remained in widespread use until about 1907, when they were replaced by more sensitive electrolytic and crystal detectors. Paul de Casteljau (born 1930 in Besançon, France.)  is a French physicist and mathematician.  In 1959, while working at Citroën, he developed an algorithm for evaluating calculations on a certain family of curves, which would later be formalized and popularized by engineer Pierre Bézier, and the curves called De Casteljau curve or Bézier curves. De Casteljau's algorithm is widely used, with some modifications, as it is the most robust and numerically stable method for evaluating polynomials.  Other methods, such as Horner's method and forward differencing, are faster for calculating single points but are less robust.  De Casteljau's algorithm is still very fast for subdividing a De Casteljau curve or Bézier curve into two curve segments at an arbitrary parametric location. André Pochan (born in 1891 in Fourmies in the north of France -? )  was a French physicist and mathematician and Egyptology enthusiast.  He taught at Cairo High School from 1930 to 1937.  In 1934 he investigated the coloration of the Khufu and Khafra pyramids.  Deported to Mauthausen in 1943, he survived the death camps and, as such, he was awarded the Medal of the Resistance and Commander of the Legion of Honor.  His main research focused on the Egyptian pyramids, especially the pyramid of Cheops, and he became known as a "highly independent pyramid scholar".  His research was highly criticized by the Egyptologist Jean-Philippe Lauer.  In 1971 he published "L 'Enigme de la Grande Pyramide" (Robert Laffont, Paris). Alfred-Marie Liénard (2 April 1869 in Amiens – 29 April 1958 in Paris), was a French physicist and engineer.  He is most well known for his invention of the Liénard–Wiechert potentials. André-Marie Ampère ( ; ] ; 20 January 177510 June 1836) was a French physicist and mathematician who was one of the founders of the science of classical electromagnetism, which he referred to as "electrodynamics".  He is also the inventor of numerous applications, such as the solenoid (a term coined by him) and the electrical telegraph.  An autodidact, Ampère was a member of the "Académie des sciences" and professor at the "École polytechnique" and the "Collège de France". D'Alembert's principle, also known as the Lagrange–d'Alembert principle, is a statement of the fundamental classical laws of motion.  It is named after its discoverer, the French physicist and mathematician Jean le Rond d'Alembert.  It is the dynamic analogue to the "principle of virtual work for applied forces" in a static system and in fact is more general than Hamilton's principle, avoiding restriction to holonomic systems.  A holonomic constraint depends only on the coordinates and time.  It does not depend on the velocities.  If the negative terms in accelerations are recognized as "inertial forces", the statement of d'Alembert's principle becomes "The total virtual work of the impressed forces plus the inertial forces vanishes for reversible displacements".  The principle does not apply for irreversible displacements, such as sliding friction, and more general specification of the irreversibility is required. Denis Papin (22 August 1647 – c. 1713) was a French physicist, mathematician and inventor, best known for his pioneering invention of the steam digester, the forerunner of the pressure cooker and of the steam engine.
Answer: André-Marie Ampère