Types of quantum field thories
What is called geometrical optics is an approximate theoretical treatment of wave optics in the short wavelength limit. The wave equation of physical optics is thus replaced by the so called eikonal equation.
Integrals involving exponential function with rapidly oscillating phase have main contributions close to the classical paths which in optics correspond to the light rays of geometric optics. However the geometric optics can tell much more than the crude light ray representation, for example the asymptotic behaviour of light near caustics and phase jumps when passing through focal points.