Bragg, William Lawrence (1862-1942), a British physicist, developed methods that made it possible to determine the atomic structure of crystals. Along with his father, William Henry Bragg, he laid the foundation for X-ray crystallography. For their work with X rays and crystals, the Braggs shared the 1915 Nobel Prize in physics.
William Lawrence Bragg was born on July 2, 1862. Bragg's father was a professor of physics and mathematics at the University of Adelaide. His mother, Gwendoline Todd Bragg, was the daughter of South Australia's postmaster general and government astronomer. William Lawrence Bragg's first encounter with X rays occurred when he was quite young. In 1895, the discovery of X rays by German physicist Wilhelm Conrad Roentgen was announced. A few weeks later, William Henry Bragg constructed a crude X-ray machine. The machine came in handy a short time later when 5-year-old William Lawrence fell off his tricycle and hurt his elbow. The X-ray machine was used to determine the extent of the young boy's injury. This was the first recorded use of X-ray medical diagnosis in Australia.
Bragg was a quiet child who liked to collect shells and enjoyed natural sciences. A species of cuttlefish that he discovered, Sepia braggi, was named in his honor. He was the oldest of three children. He and his younger brother, Robert, enjoyed turning pieces of discarded scraps into mechanical devices.
After receiving his secondary schooling at St. Peter's College in Adelaide, Bragg enrolled at the University of Adelaide when he was 15 years old. In 1908, he graduated with first-class honors in mathematics. The following year, Bragg's father accepted a position as professor at the University of Leeds, and the family relocated to England. Bragg enrolled at Trinity College, Cambridge, and began studying mathematics, but on the recommendation of his father, he later changed his concentration to physics. In 1912, he graduated with first-class honors in natural sciences. He then began research at the Cavendish Laboratory under the guidance of Joseph John Thomson. That fall, Bragg and his father began a collaboration that would result in winning the Nobel Prize and creating a new scientific field.
The Braggs became interested in the findings of Max Theodor Felix von Laue, who earlier in 1912 had discovered X-ray diffraction. Laue had discovered that when X rays passed through a crystal, they bent. This observation provided vital clues about the nature of X rays, because the patterns Laue described could only be made by waves. For years, scientists had been debating whether X rays were particles or waves, with the elder Bragg believing that X rays were beams of particles. However, as father and son began discussing Laue's findings, the younger Bragg became convinced that Laue was correct, but Laue's explanation of the diffraction was incorrect and unnecessarily complex. He reasoned that since atoms of a crystal are arranged in a pattern, the reflected X rays might reveal the arrangement of the atoms within the crystal. He then devised a mathematical equation that allowed him to study the structure of a variety of crystals. The simplified calculations that William Lawrence Bragg devised became known as Bragg's Law.
The Braggs spent two years in their joint investigations. Each brought different skills to the effort. The elder Bragg had a strong experimental background. The younger Bragg had a strong interest in crystals and a deep understanding of crystals and atomic reflection. In order to conduct the precise measurements that were required in their investigations, William Henry Bragg invented the X-ray spectrometer. One of the first substances that William Lawrence Bragg investigated was sodium chloride, or table salt. At the time, scientists thought that all chemical compounds were made up of molecules composed of atoms. Through his research, Bragg was able to show that sodium chloride in solution was made up of ions, or charged atoms of sodium chloride, and not molecules. This finding added to the scientific understanding of solutions.
The collaboration between father and son ended with the outbreak of World War I (1914-1918) in 1914. Bragg volunteered for the military and began his service in the artillery battery. He then worked as a technical adviser on sound ranging, a method to locate the enemy from the sound of gunfire. He was on duty in France when he heard that he had won the 1915 Nobel Prize. At 25 years old, he was the youngest laureate ever. Because of the war, the award ceremonies were canceled that year, and Bragg delivered his Nobel Lecture in 1922. In 1965, 50 years after Bragg received the Nobel Prize, the Nobel Foundation celebrated the occasion by inviting him to speak about developments in his area of study. This presentation was the first Nobel guest lecture.
When World War I ended, Bragg resumed his career in physics and returned to Trinity College as a lecturer. In 1919, he accepted the appointment as Langworthy Professor of Physics at the University of Manchester, a position that had been previously held by Ernest Rutherford. In 1921, he and Alice Grace Jenny Hopkinson married. The couple had four children.
While working to build a solid research institution, Bragg also continued to use X rays to study the structures of crystals. He published a list of atomic radii, but the numbers had been slightly miscalculated and later needed correcting. He also worked with several other scientists to determine absolute intensity measurements.
Bragg next spent several years investigating the complex structures of the silicate family of minerals. His findings in that area, which were completed around 1930, were of vital importance in the field of mineralogy. In addition to his own research, Bragg was instrumental in encouraging and overseeing investigations of metals and metal alloys. This work proved useful in industrial applications.
In 1937, Bragg was appointed the director of the National Physical Laboratory. A year later, he accepted the concurrent position as Cavendish professor of experimental physics at Cambridge.
He remained there until 1954, with only a temporary interruption during World War II (1939-1945), when he acted as a liaison with Canada and the United States. While at Cambridge, Bragg headed a research team investigating complex globular proteins, which went on to have spectacular success in the 1950's.
In 1954, Bragg left Cambridge for the Royal Institution, London, to become Fullerian professor of chemistry and director of the Davy-Faraday Research Laboratory, a position his father had once held. For the next 12 years, Bragg continued crystallographic research and focused much of his energy on promoting the teaching of science. He was interested in making science concepts understandable to the nonscientific community. For a time, he hosted a series of lectures on television. Following his retirement in 1966, he continued public speaking engagements. He also wrote on science topics, including a book on the development of X-ray analysis that he completed before his death in 1971.
Bragg's work had a profound effect in a number of areas, including chemistry, mineralogy, metallurgy, and molecular biology. Bragg was a pioneer in the field of X-ray crystallography. As an administrator, he had strong organizational skills and encouraged and supported the research of others. He was also a popular public speaker who had an ability to explain difficult scientific concepts in a clear manner.
In addition to the Nobel Prize, Bragg received a number of honors including the Roebling Medal of the Mineralogical Society of America (1948) and the Royal (1946) and Copley (1966) medals of the Royal Society. He held a membership in the Royal Society and honorary degrees from 11 hospitals. He helped found the International Union of Crystallography and served as the first president in 1948. He was knighted in 1941.