Equação de Klein-Gordon

$\left(\Box +{\frac {m^{2}c^{2}}{\hbar ^{2}}}\right)\psi (x,t)=0$

onde

$\left(\Box ={\frac {\partial ^{2}}{c^{2}\partial t^{2}}}-\nabla ^{2}\right)$

então

${\frac {\partial ^{2}\psi }{\partial t^{2}}}=c^{2}\nabla ^{2}\psi -{\frac {m^{2}c^{4}}{\hbar ^{2}}}\psi$

no método das diferenças finitas:

${\frac {\partial ^{2}\phi (x,t)}{\partial t^{2}}}\approx {\frac {\phi (x,t+\Delta t)-2\phi (x,t)+\phi (x,t-\Delta t)}{(\Delta t)^{2}}}$