In an electrostatic particle accelerator, an electron is accelerated from rest through a potential difference \(\Delta V\), gaining a final kinetic energy \(K_1\). A second electron is accelerated from rest through a potential difference \(4\Delta V\), gaining a final kinetic energy \(K_2\). What is the ratio \(K_2 / K_1\) of the final kinetic energy of the second electron to that of the first electron?