Jan 2nd 2017, 04:03 AM
Join Date: Jun 2016
I don't think that there is the sharp delineation you suggest,
Any "ray like" behavior is more obvious at shorter wavelengths than at longer wavelengths.
A "ray" cannot be more compact than the wavelength, so as the wavelength gets longer, any "rays" become much more spread out,
until it becomes difficult to describe them as "rays".