Science Buddies: "Ask an Expert"

Hello, I am doing the project "Using a Laser to Measure the Speed of Light in Gelatin" (https://www.sciencebuddies.org/science- ... in#summary). I have run the experiment, analysed the results and gotten ~1.37 as the index of refraction of gelatin. Using this, I was able to calculate that the speed of light in gelatin is ~218,044,953.466 meters/sec. I ran the experiment again, changing a few things (I used the same gelatin as before; I was just looking for ways to improve the accuracy of the data,) and got ~1.47 as gelatin's index of refraction, and 204,509,799.018 meters/sec as the speed of light in gelatin.

My problem is that I don't know the actual speed of light in gelatin. I've spent quite some time researching this but haven't found anything. Knowing the actual speed of light in gelatin would be extremely helpful, because I could see if the second experiment was more accurate. If that's not possible, it would still be useful to know if my results are anywhere in the vicinity of what they should be.

I appreciate any help; thanks in advance.

Hi Science_Person,

Sorry, but I wasn't able to find a source for the speed of light in gelatin either. The next best thing may be to compare some values reported for the refractive index of gelatin to compare with your results.

After a bit of online searching I found a few references that quote the refractive index of gelatin (links are listed below). Some of these appear to be results from science fair projects similar to yours. My suggestion is to find and tabulate several refractive index values available online (and cite the sources). You might show the average and range of the reported values to help indicate how your results compare.

http://cameo.mfa.org/wiki/Gelatin

https://prezi.com/mnyh8k3sihpg/the-spee ... h-gelatin/

http://www.geocities.ws/physicsexperiments/toate/4.pdf

https://prezi.com/ultzts0pnmhp/using-a- ... n-gelatin/

I hope this helps. Please ask again if you have more questions.

A. Norman

Thanks a lot, and looking at two of the links it looks like my second experiment was an improvement over the first, which is what I was aiming for. These could be really useful, so thanks!