Rayleigh, John William Strutt (1842–1919)

English physicist who wrote the standard treatise The Theory of Sound (1877–78), experimented in optics and microscopy, and, with William Ramsay, discovered argon. He was awarded the Nobel Prize for Physics in 1904 for his work on the densities of gases and the discovery of argon. He was created a baron in 1873.

Rayleigh was born in Essex and studied at Cambridge. He set up a laboratory at his home and was professor of experimental physics at Cambridge 1879–84, making the Cavendish Laboratory an important research centre.

In 1871, Rayleigh explained that the blue colour of the sky arises from the scattering of light by dust particles in the air, and was able to relate the degree of scattering to the wavelength of the light. He also made the first accurate definition of the resolving power of diffraction gratings, which led to improvements in the spectroscope. He completed in 1884 the standardization of the three basic electrical units: the ohm, ampere, and volt. His insistence on accuracy prompted the designing of more precise electrical instruments.

After leaving Cambridge, Rayleigh continued to do research in a broad range of subjects including light and sound radiation, thermodynamics, electromagnetism, and mechanics.

An inconsistency in the Rayleigh–Jeans equation, published by Rayleigh in 1900 (amended in 1905 by James Jeans), which described the distribution of wavelengths in black-body radiation, led to the formulation shortly after of the quantum theory by German physicist Max Planck.