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".
The phenomenon you are observing is called the refraction of light. Refraction occurs when light passes from one medium to another with a different refractive index, causing the light rays to change direction. In this case, the glass cylinder has a refractive index different from that of air, which causes the light to bend as it enters and exits the glass.
Now, let's consider the positioning and viewing direction. If the glass cylinder is placed above the words "Lead Oxide" with the word "Lead" closer to you and the word "Oxide" farther away, this means that the word "Lead" is located higher up on the cylinder than the word "Oxide" when viewed from the side.
When light passes through the glass cylinder and encounters the word "Lead," it undergoes refraction twice: once as it enters the front surface of the cylinder, and once as it exits the back surface of the cylinder. Each refraction causes the light rays to change direction slightly. In this case, due to the curvature of the glass cylinder, the refraction causes the light rays to converge and cross each other. This crossing of light rays is what causes the inverted appearance of the word "Lead" when viewed from the side.
On the other hand, when light passes through the glass cylinder and encounters the word "Oxide," it also undergoes refraction twice. However, in this case, the word "Oxide" is located lower on the cylinder. As a result, the refraction of light passing through the glass cylinder does not cause the light rays to cross each other, leading to the word "Oxide" appearing in the correct orientation when viewed from the side.
It's important to note that the different colors of the word "Lead" and "Oxide" are not the primary reason for the inversion or non-inversion. As you mentioned, the refractive indices of the red and blue inks are not significantly different, so the primary factor at play here is the positioning of the words on the glass cylinder relative to the viewing direction, which determines the number of internal reflections needed for viewing each word.