Today's random info is about iridescence, which according to Wikapedia is an optical phenomenon of surfaces in which hue changes in correspondence with the angle from which a surface is viewed.
Iridescence is often caused by multiple reflections from two or more semi-transparent surfaces in which phase shift and interference of the reflections modulates the incidental light (by amplifying or attenuating some frequencies more than others). This process, termed thin-film interference, is the functional analog of selective wavelength attenuation as seen with the Fabry–Pérot interferometer.
The word iridescence is derived in part from the Greek word îris, meaning rainbow,
which in turn derives from the goddess Iris of Greek mythology, who is the personification of the rainbow and acted as a messenger of the gods.
Goniochromism is derived from the Greek words gonia, which means angle, and chroma, which means color.