57 x 10 - 27 erg-sec to “a precision of about 0.5 per cent,” a value far better than had been obtained in any previous attempt. While it had been known for a long time that light falling on metal surfaces may eject electrons from them (the photoelectric effect), Millikan was the first to determine with great accuracy that the maximum kinetic energy of the ejected electrons obey the equation Einstein had proposed in 1905: namely, 1 / 2 m v 2 = h f - P, where h is Planck’s constant, f the frequency of the incident light, and P is, in Millikan’s words, “the work necessary to get the electron out of the metal.” Millikan determined h to have the value 6. Today it lends itself to different, yet complementary, readings–the judgment by physicists that the work was worthy of the Nobel Prize, and the historical insight it offers into the struggles Millikan faced accepting the very quantum theory he was validating. Millikan’s 1916 paper on the measurement of Planck’s constant was dramatic in its time. In honor of the American Physical Society’s centennial year, Physical Review Focus is publishing occasional stories describing important research published in the Physical Review throughout the past century. AIP Meggers Gallery of Nobel Laurestes Robert A.

Robert millikan atomic theory