Figure 2
From: Huygens' Principle geometric derivation and elimination of the wake and backward wave
Planar source. (a) An infinite plane with impulsive excitation, δf(t). The excitation duration or temporal pulse width is ε. The parameter z0 is the distance from the plane to a point in space, P, at which the wave field will be observed as a function of time. The propagation speed is c, where c > 0. R1 and R2 are the radii of an annulus defined by the intersection of the plane with two spheres of radii ct and c[t + ε]. The point N is the nearest point on the plane to the field point P. Each point on the plane is a point source which radiates an impulsive spherical wavelet. (b) The wave field ϕ that is propagated from the plane. (c) The wave front f in the Z + direction that is derived from the wave field which will arrive at P at t = z0/c.
