The words "CHOICE MATERIAL GLASS OXIDE" are printed in block letters, with "CHOICE" and "OXIDE" in red and "MATERIAL GLASS" in blue. These words are photographed in the top half of the figure below. When the words are photographed through a glass rod immediately in front of them their appearance changes somewhat, as can be seen in the bottom half of the figure. (The top photograph is a view looking over the glass rod at the letters.)


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The question is what is responsible for this rather unusual phenomenon?

  • (a) The dispersive effect of the difference in color causes the focusing properties of the rod to be different from red to blue.
  • (b) The rod might be different between the red and the blue letters, causing the focusing to change.
  • (c) Polarization may play an important role in causing differences in internal reflectivity that lead to different focal properties.
  • (d) Other.

After February 7th, 2014, click Read More for the answer

 The answer is (d) other. Look carefully at the photograph below of the letters viewed through the rod, but with a finger added. Does looking at the finger through the rod help you to see why some of the letters appear upside down?


In fact, all of the letters are inverted - however, the red ones are symmetric about the horizontal centerline of the letters, so they look the same normal and upside-down.

Perhaps it is not necessary at this time to further debunk the other possibilities.