Physics Photo of the Week

September 28, 2012

Artificial Mirage
A wood-burning stove with a dull flat top sits in the foreground of this image.  The background (in addition to all the kitchen clutter) shows a white knob for the dishwasher (across the room) plus a little bit of reflection from the top of the stove.  The top of the stove has a dull finish.  However, the stove had a fire in it heating the top and the walls.  The air immediately over the top of the stove is considerably warmer than the rest of the air in the room.  As a result the grazing light from the dishwasher knob is refracted and bent upwards as if it were reflected from a perfectly polished mirror.  This is the same phenomenon that gives the illusion of water on a pavement on a dry day PPOW September 21, 2007) and reflections of shore features on a lake (PPOW September 28, 2007). 

The photo at right shows an automated sequence looking through the mirage.  In the first frame the camera is well above the level of the stove top, and there is no mirage because the angle of reflection is too large for the refractive index of the stove's hot air.  The next two frames show the results when looking at a much more grazing angle.  The complete refraction of the light prevents the stove-top from being seen.  Notice that the other controls on the distant dishwasher are also distorted due to the refraction by the hot air close to the hot stove surface.


Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to dcollins@warren-wilson.edu.

All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion.  These photos and discussions may be used for private individual use or educational use.  Any commercial use without written permission of the photoprovider is forbidden.

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