Physical Review
An Experimental Investigation of de Broglie's Equation
J. G. Tappert
Abstract
The validity of de Broglie's equation is checked experimentally for electrons of 24 to 64 electron-kilovolts energy. The experiment consists essentially of deflecting a beam of cathode rays by an electrostatic field and, keeping the deflection constant, determining the relation between the intensity of the deflecting field, $V$, and the de Broglie wave-length, $\ensuremath{\lambda}$, of the deflected electrons. On the assumption that the motion of the electrons is in accordance with the laws of relativistic mechanics, and that the de Broglie wave-length is inversely proportional to the momentum, it is shown theoretically that the expression ${\ensuremath{\lambda}}^{2}V{(1+\frac{{h}^{2}}{{{m}_{0}}^{2}{c}^{2}{\ensuremath{\lambda}}^{2}})}^{\frac{1}{2}}$ should be independent of $\ensuremath{\lambda}$. Within the limits of experimental error this expression is found to be independent of $\ensuremath{\lambda}$, thereby demonstrating that the de Broglie equation, $\ensuremath{\lambda}=\frac{h}{\mathrm{mv}}$, combined with the relativity expression for $m$, is adequate to describe the facts.