Physics Photo of the Week

Quiz answer and explanation.  Dec. 3, 2004

Correct answer:   B.  The inside of an air track.

The photo at the left shows an air track in the Physics lab.  The Physics Photo of the Week (reproduced on the right) is  made from looking down the inside of the rectangular pipe. The camera was positioned on the left end of the track looking toward the large air hole for the air supply.  The smooth extruded aluminum of the hollow air track forms fairly smooth mirrors.  The image at the right shows multiple images of the single hole being reflected by the inside walls of the air track.  The bright image in the center is the direct image, all the other holes in the image are reflections and multiple reflections off the inside walls like a kaleidoscope.  Notice how the hole images on the periphery are fainter and more blurred due to loss of light and clarity with each reflection.
The image at the right is a similar kaleidoscope image, but looking down the air track from the air hose end.  The  inside corners of the air track  have been drawn on the image to  help see the origin of the  multiple images.

All images here and on the previous page were photographed by physics assistant: Dan Sockwell.

A similar kaleidoscope image was published on PPOW May 7, 2004.

Donald F. Collins