Explaining the Infinite Reflection of a Pencil in Mirror Photography

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SUMMARY

This discussion focuses on the phenomenon of infinite reflection using flat mirrors in photography, specifically involving a pencil placed between two mirrors. The reflections become progressively darker due to multiple reflection surfaces, with the first reflection being dim from the glass front surface, the second stronger from the metallic backing, and subsequent reflections diminishing in intensity. The importance of using front-surface mirrors for accurate physics demonstrations is emphasized, as they eliminate the interference caused by the glass layer.

PREREQUISITES
  • Understanding of light reflection principles
  • Familiarity with ray tracing techniques
  • Knowledge of mirror types, specifically front-surface and back-surface mirrors
  • Basic photography concepts related to light and exposure
NEXT STEPS
  • Research the principles of ray tracing in optics
  • Learn about the differences between front-surface and back-surface mirrors
  • Explore the effects of multiple reflections on image quality
  • Investigate techniques for capturing light phenomena in photography
USEFUL FOR

Students in physics or photography, educators demonstrating optical phenomena, and anyone interested in the practical applications of light reflection in visual arts.

intimidckfan
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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?
 
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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...
 

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