Introduction to Reflection and Refraction

Objective
Experience the light travels between two materials and verify the Snell's Law.

Procedure
part 1: light travels from air to glass

 Put the circular protractor under the glass, and set up the light source.

Measure the angles between the incident, and refractive lights to the normal line.

Data for part 1

θ1	θ2	sin θ1	sin θ2
0	0	0	0
10	5	0.17	0.09
15	11	0.26	0.18
20	12	0.34	0.21
25	17	0.42	0.29
30	19	0.5	0.33
40	23	0.64	0.39
50	27	0.77	0.45
60	35	0.87	0.57
70	39	0.94	0.63

part 2: light travels from glass to air

Set up the equipment as showed and measure the angles just like we did for part1

Data for part 2

θ1	θ2	sin θ1	sin θ2
0	9.5	0	0
5	9.5	0.09	0.17
10	16.5	0.17	0.28
15	24.5	0.26	0.41
20	30	0.34	0.5
25	44	0.42	0.69
30	51.5	0.50	0.78
35	64.5	0.57	0.90
40	80	0.64	0.98

Conclusion

By graphing the sin θ1 _vs sin θ2 ,  we found the ratio of the index of refraction n2/n1. (n1sin θ1=n2sin θ2) For air, n1 is 1, so the slope of the graph should be the index of refraction of the glass, which is close to 1.5. In part 2, we found out that we can't get any refraction anymore after going up to some certain angle. The critical angle we found was about 43 degree. To calculate the theoretical value, we say, n2*sinθ2=1*1 (because the max of sin is 1)  Solve for θ2 and we found that θ=41.8 degree, which is very close to the measured value.