John William Rayleigh (Strutt) (12.11.1842 —30.06.1919) was an English physicist and a Fellow of the Royal Society (1873), its president in 1905–08. Born in Langford Grove. Graduated from the University of Cambridge (1865), where he worked at Trinity College until 1871. In 1871 he equipped his own laboratory on his family estate at Terling. In 1873, after the death of his father, he inherited the title of Lord Rayleigh. In 1879–84 he was professor and director of the Cavendish Laboratory, and in 1887–1905 professor at the Royal Institution in London. From 1908 he was president of the University of Cambridge. His work was devoted to the theory of oscillations, of which he was one of the founders, acoustics, the theory of thermal radiation, molecular physics, hydrodynamics, electromagnetism and optics. He studied the oscillations of elastic bodies (strings, rods, plates), established a number of properties of oscillating systems, and was the first to draw attention to self-oscillations. He studied the diffraction, scattering and absorption of waves, waves of finite amplitude and surface waves, and predicted (1885) a special kind of surface wave (“Rayleigh waves”). He extended the concepts of phase and group velocity of waves, established the relation between them and gave a formula for the group velocity.
He laid the foundations of the theory of molecular light scattering, in particular introduced the concept of the so-called Rayleigh scattering of light, established (1871) the law according to which the intensity of light scattered by a medium is inversely proportional to the fourth power of the wavelength of the exciting light (the Rayleigh law), and explained the blue colour of the sky. In 1894, together with W. Ramsay, he discovered a new chemical element, argon, and determined its properties and its place in the periodic system of the elements (Nobel Prize, 1904). In 1900 he derived the law of the distribution of radiation energy in the spectrum of a black body as a function of temperature (the Rayleigh–Jeans law). Independently of O. Heaviside he constructed the theory of the skin effect. He is also known for the Rayleigh law of magnetisation (1887) and detected the phenomenon of magnetic after-effect, or magnetic viscosity. He designed a refractometer (the Rayleigh refractometer), established the resolving power of prism and diffraction instruments, and invented the differential manometer (the Rayleigh manometer) and an instrument for measuring the intensity of sound (the Rayleigh disc).
The B. Rumford, Copley and M. Faraday Medals.