Fabry, Charles (1867-1945)

French physicist who specialized in optics, devising methods for the accurate measurement of interference effects. He took part in inventing a device known as the Fabry-Pérot interferometer. In 1913, Fabry demonstrated that ozone is plentiful in the upper atmosphere and is responsible for filtering out ultraviolet radiation from the Sun. Fabry was born in Marseille and studied in Paris at the Ecole Polytechnique and the Sorbonne. He became professor at the University of Marseille 1904. The Ministry of Inventions recalled him to Paris in 1914 to investigate interference phenomena in light and sound waves, and in 1921 Fabry became professor of physics at the Sorbonne. Alfred Pérot (1863-1925) and Fabry worked together 1896-1906 on the design and uses of their invention. It consists of two parallel plates of half-silvered glass or quartz. A light source produces rays which undergo a different number of reflections before being focused. When the rays are reunited on the focal plane of the instrument, they either interfere or cohere, producing dark and light bands respectively. If the two reflecting plates are fixed in position relative to one another, the device is called a Fabry-Pérot etalon. In 1906 Fabry began to collaborate with Henri Buisson. They used the interferometer to confirm the Doppler effect for light 1914.