# De Broglie wavelength of an electron

If an electron which already possesses some kinetic energy of $X\rm\,eV$ is further accelerated through a potential difference of $X′\rm\,V$, then is it correct to state that the electron now has a total kinetic energy of $(X+X′)\rm\,eV$? Using this information, am I allowed to substitute this value in the de Broglie equation to find the wavelength of the electron?

$$E^2 = p^2c^2 + m^2c^4$$