1902: Lenard's study: Investigation of the relationship between the frequency and the intensity of light on the one hand and the number and kinetic energy of ejected electrons on the other. Fig. 2 shows the relationship between the frequency and the kinetic energy per electron 1905: Einstein extended Planks Hypothesis that atomic oscillators could not only take up or give out energy in discrete quanta, by regarding the radiation itself as consisting of indivisible quanta or photons.1902:Lenard’s study: Investigation of the relationship between the frequency and the intensity of light on the one hand and the number and kinetic energy of ejected electrons on the other. Fig.2 shows the relationship between the frequency and the kinetic energy per electron. 1905 :Einstein extended Plank’s Hypothesis that atomic oscillators could not only take up or give out energy in discrete quanta, by regarding the radiation itself as consisting of indivisible quanta or photons