Dew, Mirrors & Planets

The Internet is awash with images of the March '12 Venus/Jupiter conjunction - but none like this!

Laurent Laveder (Pixheaven, Photoghraphe) pictured the planets reflected in a mirror. The mirror had dew. The result, an exquisite set of coloured rings passing across Venus & Jupiter.

These are “Quételet fringes or rings”.

They do not need a planet, the sun, moon or a lamp will do. They can be found on dusty or bedewed windows and mirrors. Dusty or pollen strewn still lakes also show them.

Image ©Laurent Laveder, shown with permission.
Quételet rings and colours are generated when small micron-sized particles or water drops rest on or are close to a reflecting surface.

Light, in this case from Venus and Jupiter, reaches the drop along two routes, (A) directly and (B) after being first reflected from the surface.

The drop scatters the incident light waves predominantly forwards into a series of outgoing spherical waves. The two sets of outgoing waves overlap and combine.

In directions where the overlapping wave fronts have the same amplitude direction (in phase) they reinforce and there is light. In some other directions the waves are out of phase and they cancel each other out. The cancellation or interference condition is wavelength dependent and so the resultant fringes are coloured.

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