Reflection and Refraction

In this experiment, we begin looking at light waves and how they refract. We had a light box with a narrow slot to let a thin ray of light out, a protractor, and a semicircular clear plastic disk.

For the first set of data, we had the light entering the flat side of the disk, and exiting the curved side. We recorded the angles of incident and refraction as theta 1 and 2 respectively. 

Trial	ϴ_1	ϴ_2	sin(ϴ_1)	sin(ϴ_2)
1	5	4	0.087156	0.069756
2	10	7	0.173648	0.121869
3	15	10	0.258819	0.173648
4	20	12.5	0.34202	0.21644
5	25	16	0.422618	0.275637
6	30	19	0.5	0.325568
7	40	26.5	0.642788	0.446198
8	50	31	0.766044	0.515038
9	60	35	0.866025	0.573576
10	70	39	0.939693	0.62932

When we plotted the SINE of the angles against each other, we got a nearly perfectly linear trendline.

For our second data set, the incident ray entered on the curved side and exited on the flat side of the half-disk. At 45 degrees for the incident angle, no light exited the plastic disk.

Trial	ϴ_1	ϴ_2	sin(ϴ_1)	sin(ϴ_2)
1	0	0	0	0
2	5	7.5	0.087156	0.130526
3	10	16	0.173648	0.275637
4	15	23	0.258819	0.390731
5	20	32	0.34202	0.529919
6	30	48	0.5	0.743145
7	35	63	0.573576	0.891007
8	40	75	0.642788	0.965926
9	45	75	0.707107	0.965926

When the sin of these two angles were plotted against each other, the graph was exactly the same, except the axes were reversed.

The slope of theses lines must represent the ratio for the index of refraction of the materials. Since the index n for air is 1 we could easily figure out the refraction index for the plastic.