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Measuring Sugar Content of a Liquid with a Laser Pointer
Posted: Mon Jan 09, 2012 4:05 pm
by Anubis326
I have been having some problems with this project when I attempt the experiment. The laser is meant to something like this:
https://www.sciencebuddies.org/mentorin ... img036.jpg , but it isn't. The laser is actually coming out on the wrong side, and when it is filled with liquid the laser no longer comes out the back of the prism, instead it just shoots out both sides of the prism. I cannot figure out why this is happening or how to fix it, any help you can give would be greatly appreciated!!
Re: Measuring Sugar Content of a Liquid with a Laser Pointer
Posted: Tue Jan 10, 2012 8:18 am
by deleted-71882
Hello Anubis326,
I think you may be observing "total internal reflection" inside your prism. See
http://hyperphysics.phy-astr.gsu.edu/hb ... otint.html for a complete description.
If this is the problem, then you may be able to fix it by changing the angle at which you have the laser enter the prism. You might also have to make a prism with a smaller included angle.
Shine the laser perpendicular to the nearest side. The laser beam should enter the prism with no bending at all. If it still reflects from the opposite side, then you need a prism with a smaller angle so that the beam hits the opposite side at less than the critical angle.
Good luck, WW
