3/25 Introduction to Reflection and Refraction

Purpose

The purpose of this experiment was to explore the law of reflection, refraction, and total internal reflection.

Part A

 

Light ray box faced to the flat side of the len

 

 

Trial	θ1 (±1)	θ2 (±1)	sin θ1 (±0.02)	sin θ2 (±0.02)
1	0	0	0	0
2	5	3	0.09	0.05
3	10	6	0.17	0.10
4	15	8	0.26	0.14
5	20	13	0.34	0.23
6	25	14	0.42	0.24
7	30	18	0.50	0.31
8	35	22	0.57	0.37
9	40	26	0.64	0.44
10	45	27	0.71	0.45
11	50	28	0.77	0.47
12	55	31	0.82	0.52
13	60	33	0.87	0.55
14	65	35	0.91	0.57
15	70	36	0.94	0.59

 

 

 

The slope of this graph is the index of refractive glass, which is 1.56.

n₁sinθ₁= n₂sinθ₂

sinθ1_/ sinθ2 _{= n2/n1 = n glass/ n air= n glass.}

 

Part B

 

 

Light ray box faced to the curve side of the len

 

 

Trial	θ1 (±1)	θ2 (±1)	sin θ1 (±0.02)	sin θ2 (±0.02)
1	0	0	0	0
2	5	9	0.09	0.160
3	10	17	0.17	0.292
4	15	24	0.26	0.407
5	20	34	0.34	0.560
6	25	40	0.42	0.643
7	30	51	0.50	0.778
8	35	60	0.57	0.867
9	40	77	0.64	0.974

 

The slope of this graph is the reciprocal value of the index of refrative glass, which is 0.67.

n₁sinθ₁= n₂sinθ₂

sinθ1_/ sinθ2 _{= n2/n1 = n air/ n glass= 1/ n glass}

n₁sinθ_critical= n₂sin90

θ_{critical = asin(n2}sin90_{/n1) = 42 degress}

Conclusion

 

      The index of refrative of glass was determined to be 1.6, and product of the slope in case 1 and 2 was 1 because their relationship is inversed. In case 2, we could not get a refraction when the incident angle was larger than 40 degress because it reached to the critial angle for a total internal reflection, which means there is only reflection and no refraction once the incident angle is greater and equal to the critical angle, and the critical angle was calculated to be 42 degress for this glass.