Quetelet rings

Quetelet rings are an optical interference pattern that appears on an illuminated reflective surface covered by fine particles, such as dust on a mirror.

[1] Quetelet rings form due to wave interference between light that is first scattered by a particle and then reflected off the surface, and light that is first reflected by the surface and then scattered by the particle.

When illuminated by white light, the patterns for different wavelengths become slightly misaligned, producing colored rings.

These rings are most visible around the reflection of the light source, and their size depends on the proximity of the light source and observer to the surface, as well as the distance between the particles and the reflective surface.

A video demonstrating Quetelet rings on a mirror covered in flour, with the flashlight moving around the observer.