A Determination ofemfor an Electron by Direct Measurement of the Velocity of Cathode Rays

The velocity of cathode rays, driven by potentials of from 10,000 to 20,000 volts, is measured directly by timing the passage of the electrons between two localized transverse high-frequency electric fields 75 cm apart. Those electrons which pass undeflected travel the distance between the deflecting fields in an even multiple of half a cycle of the oscillating fields. The velocity thus obtained, combined with the expression for the energy imparted to an electron in falling through a measured difference of potential, gives the value of $\frac{e}{m_0}$.