Theodore Lyman graduated from Harvard in 1897, and completed a Ph.D. there in 1900. Except for two years at the Cavendish from 1900 to 1902, he remained at Harvard for the duration of his career. He resigned as professor and chair of physics in 1926, but continued as director of the Jefferson Laboratory for 20 more years.
Upon his retirement, a new physics facility was named the Lyman Labora-tory of Physics. Lyman was a pioneer in studying the extreme ultraviolet. Theodor Schumann in Leipzig had extended spectroscopy to about 200 nm by using a fluoride prism; Lyman substituted instead a concave grating in a vacuum spectrometer.
In 1906, he studied the molecular spectrum of hydrogen. In 1914, he discovered the ultraviolet atomic series of hydrogen that had been predicted by Ritz from Balmer’s visible series. Later, he also investigated the principal series of helium (including the Lyman alpha line used by astronomers to study the sun). By 1940, he had reached 10 nm, nearly closing the gap between ultraviolet and X-rays. Lyman received the Ives Medal from OSA in 1931.
The famous Indian physicist Chandrasekhara Venkata Raman received a B.S. in 1904 and an M.S. in 1907 from Presidency College, Madras. Because scientific research was almost completely neglected in India, Raman did not focus his initial career in physics. Instead, he took a civil service post in the finance department in Calcutta in 1907, and continued his scientific work in his spare time.
Over the next decade, he published some 30 papers (many in optics) in Nature, Phil. Mag. and Phys. Rev.—which helped to make his name familiar outside of India. In 1917, he was offered a physics appointment at Calcutta University. This marked the beginning of a very productive time in Raman’s life, which he termed his “golden era.” It extended from 1917 until 1933 and included multidisciplinary research in optics, acoustics and other branches of physics.
In 1918, Raman published a book on the molecular diffraction of light, which led him to his 1928 discovery of the Raman effect. Using a very simple apparatus, he found that, when a beam of monochromatic light is scattered by a transparent medium, the scattered light has weak components of changed frequency, with the shift characteristic of the substance causing the scattering. Other scientists quickly verified his published results.
Raman was knighted in 1929 and awarded the Nobel Prize in physics in 1930. From 1933 until his death in 1970, he continued his research at his laboratory in Bangalore, writing a book on the physiology of vision in 1968. He was venerated as the father of Indian science.
Robert Williams Wood was born in Concord, Mass., and studied at Harvard and Berlin. He taught physics at the University of Wisconsin from 1897 until 1910, when he became professor of experimental physics at Johns Hopkins. He studied problems of diffraction and interference and produced blazed echelette gratings for infrared radiation.
He did much work on the fluorescence and resonance spectra of sodium vapor and of iodine, and devised experiments for observing anomalous dispersion. He was an experimenter of great ingenuity and introduced many instrumental improvements. His text Physical Optics became the most widely used book on the topic. (It was reprinted in 1988 by OSA.) He received the Ives Medal from OSA in 1933.
A native of Illinois, Robert Andrews Millikan studied physics at Oberlin and later at Columbia, followed by a postdoc in Germany. In 1896, he joined the physics faculty at the University of Chicago. He taught and wrote textbooks for 10 years. In 1907, he began taking measurements of the electronic charge, e. Earlier researchers had studied the behavior of clouds of charged particles, but he investigated single drops of water (1909) and oil (1912) in electrical and gravitational fields. From those, he derived the first accurate value of e, and the best one to be used for quite some time.
Although important, Millikan’s achievements up to this point were not within the realm of optics. (However, he did have to use X-rays to ionize the particles, and a microscope system for determining when the upward electrical pull on the ionized particle just balanced its tendency to fall in air.) His major optics contribution was in 1916, when he turned his attention to the photoelectric equation of Einstein (E =hv).
By varying both energies and frequencies, he obtained an accurate value for the Planck constant h. For his determinations of e and h, he was awarded the Nobel Prize in physics in 1923. He also did much subsequent work on cosmic rays. From 1921 until 1945, he was chairman of the California Institute of Technology.
Arnold Sommerfeld studied mathematics at the university in Konigsberg, Germany, the town where he was born. After brief positions at Gottingen, Clausthal and Aachen, he became a professor of theoretical physics—and the successor to Boltzmann—at Munich (1906 to 1931). His most famous work belongs to the Munich period.
He then turned to the study of atomic spectra. In 1915, he suggested that the circular orbits of the Bohr atom should instead be elliptical ones and postulated a new, azimuthal quantum number to specify these ellipses. He introduced an additional magnetic quantum number to explain the Zeeman effect. He also predicted fine-structure lines, which were confirmed by Paschen in 1916.
His first detailed book on wave mechanics appeared in 1929. An inspiring teacher, he was said to have trained more Nobelists than any other professor of his time, although he himself was never awarded that prize. After the Nazis came to power in 1933, he vigorously defended his Jewish colleagues and was denounced by the authorities and forced into retirement. He died in Munich in a tragic accident. His lectures on physics and optics, published as books, remain as lucid, valuable texts.
[ John N. Howard is the founding editor of Applied Optics and retired chief scientist of the Air Force Geophysics Laboratory. ]