Einstein’s Theory of Photoelectric Emission

In 1905, Einstein proposed a simple but revolutionary explanation for the photoelectric effect. He assumed that light consists of bundles of energy, called photons and viewed photoelectric effect as a collision between a photon and a bound electron. The energy E of a single photon is given by   E = hv

                                  Robert A. Millikan (1868-1953)

Robert Andrews Millikan was born on March 22, 1868 in U.S.A. During his undergraduate course, his favorite subjects were Greed and Mathematics. But after his graduation in 1891, he took, for two years, a teaching post in elementary physics. In this period, he developed interest in the subject. He received his Ph. D. (1895) for research on polarization of light emitted by incandescent surfaces.

Millikan spent a year (1895-1896) in germany, at the Universities of Berlin and Gottingen. He returned at the invitation of A.A. Michelson to take appointment as his assistant at the newly established Ryerson Laboratory at the University of Chicago (1896). He became professor at that University in 1910, a post which he retained till 1921. As a scientist, millikan made numerous momentous discoveries in the fields of electricity, optics, and molecular physics. His earliest major success was the accurate determination of the charge carried by an electron, using the elegant “falling-drop method”. He also proved that this quantity was a constant for all electrons demonstrating the quantized nature of charge.He also verified experimentally Einstein’s photoelectric equation, and made the first direct photoelectric determination of Plank’s constant h. thoughout his life, Millikan remained a prolific author, making numerous contributions to scientific journals. He was awarded the Noble Prize in Physics in 1923.