Explaining the Infinite Reflection of a Pencil in Mirror Photography

[intimidckfan]

I have a project in school in which I have to take a picture of a physics phenomenon that has to do with light and reflection. So I was thinking to use flat mirrors and put two of them in front of each other. How would I explain why the pencil I put in the middle is reflected infinitely and that it gets darker as it goes into the mirror images?

 

[berkeman]

Use ray tracing and talk about the efficiency of each reflection. BTW, unless you are using front-surface mirrors, you will get multiple reflections from each mirror surface. The first (dim) one from the front surface of the glass, the second (stronger) one from the metallic reflection surface, the third (dimmer) one from the re-reflection inside the mirror back from the inside of the glass, to the metallic surface, and back out of the glass, etc.

You should talk about the difference in reflection quality in your project too. Talk about why first-surface mirrors are used for real physics work...