Sirs William and Lawrence Bragg. This portrait was taken just before Sir Lawrence's broadcast on X-ray metals, delivered from London on February 23rd, 1942. This was the only occasion on which two Nobel laureates, father and son, took part jointly in a broadcast. William Henry Bragg (1862-1942) was an English physicist, chemist, mathematician and active sportsman who uniquely shared a Nobel Prize with his son William Lawrence Bragg, the 1915 Nobel Prize in Physics. The mineral Braggite is named after him and his son. William Lawrence Bragg (1890-1971) was an Australian-born British physicist and X-ray crystallographer, discoverer (1912) of the Bragg law of X-ray diffraction, which is basic for the determination of crystal structure. To date (2012), Lawrence Bragg is the youngest Nobel Laureate.