# Difference between revisions of "Dictionary:Eikonal equation"

(ī kōn’ ∂l) A form of the wave equation for harmonic waves in which the local velocity ${\displaystyle V}$ is compared to a reference velocity ${\displaystyle V_{R}}$(analogous to comparing a velocity to the speed of light in vacuum):
${\displaystyle \left(\nabla \phi \right)^{2}=\left({\frac {V}{V_{R}}}\right)^{2}=n^{2}}$,
More commonly in geophysical literature, the eikonal equation is written in terms of medium velocity only ${\displaystyle V(\mathbf {x} )}$
where $\displaystyle \mathbf{x} = (x_1,x_2,x_3), as