Spherical Wave

Plane Wave but the surface of propogation is spherical instead of planar.

Observing a Spherical (Light) Wave from $(x,y,z)$ while at $(x^{\prime },y^{\prime },z^{\prime })$

$$E(\vec{r},t)\propto E_0\frac{\exp (i(kr-\omega t)}{r}$$ $$r=\sqrt{(x^{\prime }-x{)}^2+(y^{\prime }-y{)}^2+(z^{\prime }-z{)}^2}$$

See Fresnel Diffraction