Physicist — John William Strutt, third Baron Rayleigh (Langford Grove, 1842 – Terling Place, 1919), was a British physicist, Nobel Prize in Physics in 1904. A nobleman and landowner, he set up a laboratory on his estate and for years directed the celebrated Cavendish Laboratory at Cambridge. He made contributions to acoustics, optics and wave theory: his treatise “The Theory of Sound” is a classic, and he explained the scattering of light by air molecules (Rayleigh scattering), which gives rise to the blue of the sky. In studying blackbody radiation, the Rayleigh–Jeans law highlighted the so-called “ultraviolet catastrophe”, one of the problems that led Planck to quantum theory. He received the Nobel Prize for the discovery of argon, a noble gas identified together with William Ramsay thanks to extraordinarily accurate air-density measurements.
Trivia
Rayleigh discovered argon because he noticed a tiny but persistent density difference between nitrogen extracted from air and that produced chemically: that discrepancy revealed an unknown gas hidden in the atmosphere.
Theories and contributions
- Rayleigh scattering — Light is scattered by molecules in a way inversely proportional to the fourth power of the wavelength (), giving the sky its blue colour.
- Rayleigh–Jeans law — Blackbody energy density in classical physics: , valid at low frequencies but the cause of the “ultraviolet catastrophe”.
- Discovery of argon — Identification of the noble gas argon (1894) through air-density measurements, together with William Ramsay.
Featured in chapters
Linked atoms
2 linked atoms.