How to measure refractive index of a clear solid? I have a few clear solids I need to measure refractive index on. For example PMMA (acrylic) has a refractive index of approximately 1.48. I suspect that it has to do with projecting a laser through the material at an angle and measuring the resulting angle after the laser passes through the material.
Any help would be appreciated.
 A: The most accurate way to do this simply would be to use the Brewster angle.
You set up your sample with a laser that is polarized perpendicular to the surface; then you measure the reflection as a function of angle of incidence. You get a clear null in the reflection at just one angle - the Brewster angle.
This is a simple enough experiment to do if you have a photocell: plotting the intensity as a function of angle you can find the zero. If you want, you can even use a cylindrical lens to expand the laser beam in just one direction, and then you will get all angles of reflection measured at the same time; that makes determining the refractive index really easy.
It really depends on the shape of your sample (I am assuming a planar sample here). If you have certain "other" shapes (for example, a prism) you might be able to determine the angle at which total internal reflection happens; that is a sensitive measure of the refractive index. With a prism it is also possible to measure the total angle of deviation as you go through the sample; this will give you a reasonably good measurement. And if the sample is very thick but perfectly planar, then the lateral deviation of a beam passing through the sample becomes workable - but it tends to be a rather poor measure. 
Most samples will have a refractive index that is a function of wavelength - if that is important, you will have to use white light, and measure the deviation through a prism to get the range of values.
