Here I briefly describe an alternative method of verifying Snell's Law using a semicircular block and pins. Two pins are placed along a radius and a third pin placed on the other side to locate the ray as shown.The problem with this method is that the curved surface of the block distorts (magnifies) the pins. To avoid this the two pins have to be close to the block thus limiting accuracy.
The advantage as I see it is that the arrangement is fairly easy to understand and relate to the theory because refraction only occurs at one boundary. After drawing in the rays the angles of incidence and refraction are easily measured. With care I was able to get satisfactory results.
I believe that sometimes the details of an experiment can confuse and distract students who cannot easily relate it to theory and hindering learning. One example of this I can remember from my student days is the method of mixtures for finding specific heat capacity.
