Measuring the Refractive Index of a Glass Prism
Aim: Determine the relationship between angle of incident and angle of refraction of a glass
prism and hence find the refractive index of the prism.
Method:
1. Prepare a laser and a glass prism on a white paper
2. Trace the prism on the white paper
3. Point the laser on the normal of the prism and make the laser go pass the
center of it.
4. Trace the refractive ray
5. Repeat step 3 and 4 with different incident angles ( 7° interval and 35° range)
Data Collection
Incident angle of
laser
θi
Δθi = ±1°
Refractive angle of the laser
θr
Δθr = ±1°
Trial 1
Trial 2
Trial 3
7
10
10
10
14
20
22
20
21
32
29
30
28
39
39
48
35
61
59
65
42
72
72
83
Refractive index of air = 1
Data Processing
Incident angle of laser
θi
Δθi = ±1°
Average Refractive angle
of the laser
θr
±Δθr (°)
sin θi
±Δθi
sin θr
±Δθr
7
10±1*
0.67±0.02
1.0±0.3
14
21±1
0.574±0.006
0.9±0.3
21
30±2
0.47±0.06
0.7±0.2
28
42±5
0.36±0.03
0.5±0.1
35
61±3
0.24±0.02
0.4±0.1
42
76±6
0.12±0.02
0.17±0.05
*Uncertainty of refractive angle of laser 10° remained 1 since the uncertainty of average was
lower than the previous uncertainty
-Calculations
1) Average refractive angle = (∑θr)/(number of values)
