The wave equation in one dimension is:
v-2∂2H/∂t2 - ∂2H/∂x2 = 0
v-2∂2H/∂t2 - (∂2H/∂x2 + ∂2H/∂y2) = 0
v-2∂2H/∂t2 - ∇2H = 0
where v is the term that describes the velocity of the wave, and H is the quantity that the wave is propogating through. Note that H can be either a vector (like the electric and magnetic fields) or a scalar (like density or pressure).