Physics — The Wave Equation

\frac{\partial^2 u}{\partial t^2} = c^2 \frac{\partial^2 u}{\partial x^2}

u(x,t) = f(x - ct) + g(x + ct)

\nabla^2 u = \frac{1}{c^2}\frac{\partial^2 u}{\partial t^2}

k = \frac{\omega}{c}