posted by Bert .
If a solid glass cylinder is placed above the words Lead Oxide (Lead in red print and Oxide in blue) and viewed from the side, the word Lead appears inverted, but the word Oxide does not. Explain.
What part of the cylinder is on top of the letters? From what direction is it viewed? The answer is not related to the different colors, because the index of refraction is not very different. It may be related to where the words are located with respect to the viewing direction. Different numbers of internal reflections may be needed to view "lead" and "oxide".