Ronald George Wreyford Norrish (1897-1978), English physical chemist. Norrish was a pioneer of photochemistry, the study of the reactions that occur when light is shone on chemicals. He developed flash photolysis in 1945, along with George Porter. This enabled unstable chemical intermediates produced in an intense flash of light to be identified from their absorption spectra, the unique pattern of light wavelengths they absorb. This allowed Norrish to follow the paths of chain reactions. It was for this work that he was awarded the 1967 Nobel Prize for chemistry. Norrish studied and then taught at Cambridge University until his retirement in 1965.