question: The Bragg–Gray cavity theory developed by Louis Harold Gray, William Henry Bragg, and a physicist that was a joint winner of the Nobel Prize in Physics in what year?
answer: 1915
context: Title: Bragg–Gray cavity theory
  Passage: According to the Bragg–Gray cavity theory, the ionization produced in a small cavity within an irradiated medium or object is related to the energy absorbed in that medium as a result of its radiation exposure.  It was developed in 1936 by British scientists Louis Harold Gray, William Henry Bragg, and William Lawrence Bragg.
  Title: Kedareswar Banerjee
  Passage: Kedareswar Banerjee (15 September 1900 – 30 April 1975) was an X-ray crystallographer and director of the Indian Association for the Cultivation of Science, Kolkata.  Early in his career he determined the structures of naphthalene and anthracene.  In 1931, he worked with Sir William Henry Bragg and developed one of the first direct methods of crystal structure determination.  He was Professor of Physics at the Indian Association for the Cultivation of Science from 1943 to 1952 and Director of the Association from 1959 until his retirement in 1965.  Between 1952 and 1959 he was Head of the Department of Physics at Allahabad University.  His interests in crystallography were widespread and, with his death, India has lost a renowned teacher.  K. Banerjee joined the research group of Sir C. V. Raman at the Indian Association for the Cultivation of Science (IACS), Calcutta, a premier Indian research institute of India.  He worked in various institutions including IACS, the India Meteorological Department, University of Dhaka and Allahabad University and finally retired as the Director of IACS, Calcutta in 1965.  Prof. Banerjee explained some points of crystal research to Homi J. Bhabha (21 Dec 1956) also .
  Title: William Lawrence Bragg
  Passage: Sir William Lawrence Bragg (31 March 1890 – 1 July 1971) was an Australian-born British physicist and X-ray crystallographer, discoverer (1912) of Bragg's law of X-ray diffraction, which is basic for the determination of crystal structure.  He was joint winner (with his father, William Henry Bragg) of the Nobel Prize in Physics in 1915: ""For their services in the analysis of crystal structure by means of X-ray"", an important step in the development of X-ray crystallography.
citations: William Lawrence Bragg Bragg–Gray cavity theory