How is Iridescence handled in a Path Tracer? I have little knowledge of this topic but from what I gather in a Ray Tracer each ray is given its own wavelength as opposed to an RGB value. This automatically simulates Dispersion and Fluorescence. Is this called Spectral Rendering?

What are the approaches usually taken to render Iridescence? Could someone give a brief overview of the method and a reference to a resource I can use to learn more in-depth knowledge I can use for implementation?
Iridesence can be seen in several variations: diffraction as seen in CDs and DVDs (see Stam's SIGGRAPH 1999 paper on this), phase shifting and modulation in multi-layered surfaces as you see in oilspills on water, or structural coloration as you see in butterfly wings. (Also there is the related pearlescence). However, it's not trivial in any way, probably worth a paper or two.