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Photographic gallery.  Thousands of particles under the microscope.
Ghosting on a wall behind a picture frame

Ghosting Behind Picture Frame

This image shows the effect of proximity on the efficiency of the deposition. The closer the frame to the wall the heavier the deposit.



"Ghosting" refers to the darkening of areas on the walls or ceiling due to the deposition of particles at specific locations. These locations are typically areas of local air turbulence or areas where the distance between two surfaces is small so that the net force of diffusion on small particles is toward the surfaces. In this case the darkening is due to the proximity of two surfaces, the picture frame and the wall. The picture was hung on the wall so that the top of the picture frame was farthest from the wall. The base of the picture frame rested directly on the wall. The wall had a slight texture so the actual contact points were few. Notice that the ghosting is darker at locations where the picture fame got closer to the wall. The effect shown here required 25 years to form. Ghosting will appear much more quickly if the turbulence is greater and if there is more soot in the environment.

Significance in the Environment:

Characteristic Features:

Associated Particles: