Louis de Broglie later (1924) suggested in his doctoral dissertation that electrons are like photons and can act as waves. The wave-like behaviour of cathode rays was later directly demonstrated using reflection from a nickel surface by Davisson and Germer, and transmission through celluloid thin films and later metal films by George Paget Thomson and Alexander Reid in 1927. (Alexander Reid, who was Thomson's graduate student, performed the first experiments but he died soon after in a motorcycle accident and is rarely mentioned.)