Science Buddies: "Ask an Expert"

I am working on this experiment --https://www.sciencebuddies.org/science- ... p009.shtml

I have the research complete and assembled all of the materials needed to conduct the experiment. But I have 2 big questions.

1. I am unsure as to exactly what angle to measure. The experiment talks about the "normal" which according to the definition provided seems unclear. I know that the angle of refraction is key to the experiment. But which angle am I to measure?

2. It says to use Snell's law to calculate the index of refraction of the gelatin and then apply the definition of index of refraction to find the speed of light in the medium. What is "the index of refraction" Can someone provide a sample equation for this experiment??

Thanks!!!

Hello Spin,

This is a good basic physics experiment that you should enjoy.

I think both of your questions can be answered by just a bit more basic research. The first page of the project description here on Science Buddies has a number of cited references. Just click on the "Background" tab and look at the bottom under the heading "To learn more about Snell’s law, try these links:" These are excellent cites that will not only explain Snell's law, but will show you diagrams that depict the angles you need to measure.

The term "normal" used in the experimental procedure is a common term in geometry. If a line is "normal" to a surface, it means it is perpendicular to the surface, or at a 90 degree angle to it. So the procedure is describing the angle to be measured is from the surface of the container to a line perpendicular, or "normal", to the side of the container. If you look at the diagrams in either of the first two cited references for Snell's law, that angle is Theta(1).

I hope this helps get you started. HAVE FUN WITH SCIENCE!