Question about sign convention for R1 and R2 when using the lens maker's formula

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SUMMARY

The discussion centers on the sign convention for radii R1 and R2 in the lens maker's formula, particularly for various lens types including convex, planoconvex, concave, planoconcave, and meniscus lenses. The key takeaway is that R1 is considered negative if it lies on the left side of the lens pole, while R2 is positive if it bulges outward from the lens. The confusion arises from differing interpretations of diagrams and definitions in various resources, including a specific online tool that provides conflicting visuals. Clear understanding of these conventions is essential for accurate optical calculations.

PREREQUISITES
  • Understanding of basic optics principles
  • Familiarity with the lens maker's formula
  • Knowledge of lens types: convex, concave, planoconvex, planoconcave, meniscus
  • Ability to interpret optical diagrams and sign conventions
NEXT STEPS
  • Study the lens maker's formula in detail
  • Research the sign conventions for optical surfaces
  • Examine various lens types and their characteristics
  • Explore online tools for calculating focal lengths and radii
USEFUL FOR

Students and professionals in optics, physics educators, and anyone involved in designing or analyzing optical systems will benefit from this discussion.

chitturp
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Hi!
I'm having some trouble with optics.
When we have convex, planoconvex, concave, planoconcave, and meniscus lenses, I don't understand how to substitute with the sign for R1 and R2. How do I determine whether the radius of a side is negative or positive? A book that I'm using said to take incident light in a particular direction and then measure the radius from the lens itself, but I honestly still don't understand that method at all... Then I found this:

http://www.livephysics.com/tools/optics/focal-length-for-thin-lens.html

but even though it says there that a surface "bulging out" of the lens is taken as R>0, and a surface "depressed into the lens" is R<0, it has the exact opposite shown in a few of the diagrams..

I'm confused and I would really appreciate it if someone could clarify this.
Thank you!
 
Science news on Phys.org
Use sign convention. For example R1 is negative if it lies on ghe left side of the pole.
 
It makes sense now! Thank you!
 

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