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Chaffee Aids Research on Absolute Determination of the Ratio of Charge of Electron to its Mass--Value Found is 1.761x10


The following article on the Cruft Laboratory research was written for the Crimson by G. W. Pierce, Rumford Professor of Physics, and director of the Cruft Memorial Laboratory.

At the Cruft Laboratory, among the numerous researches that have been under way, Miss Charlotte T. Perry, graduate student in Radcliffe College, and Professor E. L. Chaffee have completed a research on the absolute determination of the ratio of the charge of an electron to its mass. This research makes use of a direct measurement of the time required for an electron to move from one point to another under the action of a high-voltage field. The electric field was obtained by the use of the 100,000-volt storage battery belonging to the laboratory and the timing of the electron was accomplished by a short wave oscillator. The frequency of the oscillator was obtained by the use of piezo-electric standards of frequency which were also developed in the laboratory and have come into great importance commercially in the control of the wave lengths of radio transmitting stations. From the measurements of electron velocity Professor Chaffee and Miss Perry have obtained an accurate value of the physical constant e/m (charge divided by mass of electron). The value obtained is 1.761x107. An interesting fact is that this new value checks exactly a value previously computed from spectroscopic data; namely, 1.761x107--but departs markedly from the best previous experimental results 1.769, which were obtained by a magnetic deflection of the electron.

The importance of this research rests on the fact that it helps to fix the value of an electrical constant of great importance in theoretical physics.

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