Light Refraction Lab

Purpose:

The purpose of this experiment was to test the refraction of light through a class prism.  A light source was used with a circular protractor to measure the angle of refraction for the light source.

Method and Results:

A light source was set up with a focused beam of light.  A glass semi circle prism was set on a circular protractor and the light was focused into the prism at measured angles.  

First the light was incident to the strait diameter of the semicircle yielding these results.

theta i	theta r	sin(theta i)	sin(theta r)
144	60	0.587	0.866
148	55	0.53	0.819
150	50	0.5	0.766
152	45	0.47	0.707
156	40	0.407	0.643
158	35	0.375	0.574
161	30	0.326	0.5
163	25	0.292	0.423
167	20	0.225	0.342
172	15	0.139	0.259

Next the light was focused incident to the arc of the semi circle giving data table # 2.

theta i	theta r	sin(theta i)	sin(theta r)
124	30	0.829	0.5
135	25	0.707	0.423
149	20	0.515	0.342
152	15	0.469	0.259
167	10	0.225	0.174
174	5	0.105	0.087
180	0	0	0
190	-5	-0.174	-0.087
203	-10	-0.391	-0.174
211	-15	-0.515	-0.259

Conclusion:

When a graph of the two angles was taken, it was found to be linear, these results are not what was to be expected.  

A reason for both sets of theta vs. theta graphs incorrect equations is due to the fact that the results were not taken over a longer range of circular increments.  If the data was to be taken as every 10 degrees for 10 trials the results may have been less skewed.  The slope of the sin(O)1 vs sin(O)2 was taken to be the index of refraction which was 1.52 +/- .15.