The Franklin Institute Logo
Case Files logo

Dr. Robert A. Millikan: Fundamental Measurements in Electricity and Radiation, 1937

Important Discovery

Continuing experimentation led Millikan to his first important discovery of the elementary charge of electricity through use of his elegant "falling drop method" measuring the constant charge and quanta of electrons, the direct determination of Planck's Constant, confirmation of the atomic theory of matter and experiments in spectroscopy beyond ultraviolet radiation levels. Important research in cosmic radiation and ionization phenomena followed.