Low Cost, High Index of Refraction?

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Discussion Overview

The discussion revolves around finding a low-cost, safe, and transparent substance with a high index of refraction for use in an introductory physics experiment. Participants explore various materials and their refractive indices, considering both solids and liquids.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests using ice cubes (n = 1.31) and jello (n = 1.38) but notes they do not significantly vary from the typical range of 1.4 to 1.7 found in most glasses and clear plastics.
  • Another participant mentions water (n = 1.333) and questions whether only solids are needed.
  • Additional materials proposed include lead fluoride (n = 1.8), lead tungstate (n = 2.3), and bismuth germanium oxide (n = 2.15). Aerogel is also mentioned as a low index option but noted to be difficult to handle.
  • One participant raises the possibility of using liquids and references Cargille's range of optical fluids.
  • Gels are suggested as alternatives, with specific products like Astroglide and Purell mentioned.
  • There is a discussion about the characterization of the refractive index of transparent solids, with some participants arguing that the perceived narrow range is more about the definition of the index than the materials themselves.
  • Participants engage in a meta-discussion about the expression of refractive indices and light travel speeds, with some asserting that the narrow range is a property of the variable used to express it.

Areas of Agreement / Disagreement

Participants express differing views on the characterization of the refractive index range of transparent solids, with some agreeing on the narrowness of the range while others argue it is a property of the definition used. The discussion remains unresolved regarding the best materials to use for the experiment.

Contextual Notes

Some participants note that the discussion may depend on the definitions and properties of the materials considered, as well as the handling difficulties associated with certain substances.

ejensen6
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I have my introductory physics students determine the index of refraction of various solids using fairly conventional methods (lining up pins or determining critical angle). I think this experiment would be more interesting if I could vary it more. I would like to find a substance with the following properties:

* Inexpensive
* Safe
* Transparent to most visible wavelengths
* An index of refraction outside the range of 1.4 to 1.7 (almost all glasses and clear plastics seem to be in this range)

I've considered using big ice cubes (n = 1.31). Jello is about 1.38, so it's not much of a change. Cubic zirconia is over 2, but I can't find slabs of that.

Ideas?
 
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Water is 1.333. Or did you only need a solid?
 
Lead fluoride is 1.8. Lead tungstate is 2.3. Bismuth Germanium Oxide is 2.15. In the other direction, aerogel is close to 1 (but not so easy to handle).
 
Interesting problem- transparent solids have a very narrow range of refractive index. Can you use liquids at all? Cargille has a nice range of fluids:

http://www.cargille.com/opticalintro.shtml

Another option may be gels- not to be too crude, but Astroglide and Purell may work.
 
Andy Resnick said:
transparent solids have a very narrow range of refractive index.

I think that's more a property of the definition of index than anything else. I could equally well have said " transparent solids have a huge range of light travel speeds: the variation is over a range 100,000 miles per second".
 
Vanadium 50 said:
I think that's more a property of the definition of index than anything else. I could equally well have said " transparent solids have a huge range of light travel speeds: the variation is over a range 100,000 miles per second".

While true, I don't see any problem with saying it like Andy did. It is referring to the index of refraction and the scale we use for it, not the speed of light. (Obviously the two are related, but you get my point I hope)
 
Right, but my point is that the "narrow range" is a property of the variable we use to express it in. In other, equivalent expressions, its not so narrow.
 
Vanadium 50 said:
Right, but my point is that the "narrow range" is a property of the variable we use to express it in. In other, equivalent expressions, its not so narrow.

Whatever... slow day?
 
You got it...watching my code slowly compile. Slllooowly.
 

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