# Refractive Index of Perspex

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• Published : February 23, 2013

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Refractive Index of Perspex
Aim: the aim of this experiment is to find the refractive index of Perspex. Tools:

Pencil

Graph Paper

Perspex glass

Pin
Procedures:
1.
2.

3.
4.
5.
6.

Ruler
Styrofoam
Paper

Place an A4 paper over the Styrofoam, then Place the Perspex glass on the middle of the A4 paper and mark its place.
Place a pin about away from the side of the Perspex glass, Draw six points about 10 degrees away from each other as labeled from 1-6 on the right side of the pin.
Put a pin in point 1 and look through the glass and try putting a pin which is parallel to point 1.
Repeat the process and put another pin. Do this for all the points. After that draw a line from each point to the pin. Then draw a straight line passing each of the same numbered points of the removed glass . Using a Protractor find how much each angle equals from the normal ,and fill the data in a table then do the calculations and graphing needed shown in the data processing .

Data collection:
#
1
2
3
4
5
6

i1
30
40
50
60
65
70

i2
30
40
50
50
55
65

Graph of sin ������ and sin������:

������
30
40
50
55
60
67.5

r1
20
25
30
33
35
40

r2
20
25
30
33
35
40

������
20
25
30
33
35
40

sin ������
0.5
0.64
0.76
0.82
0.86
0.92

sin ������
0.34
0.42
0.5
0.54
0.57
0.64

Data processing:
������ 2−������ 1

Slope =
=

������ 2 −������ 1

0 .9−0 .4
0 .7−0.4

= 1.67
Evaluation: Conclusion:The refractive index of Perspex, acquired to calculation and the graph is 1.67, which is good compared to other results. Neither method is totally accurate, but the value from the graph is more accurate refractive index of Perspex.

 Sources of Errors:1. The incident ray and the refracted ray drawn could have been incorrect. Therefore this would be giving incorrect angle results. 2. The block might not have been drawn correct and thus causing incorrect results..

3. Not very accurate as putting the pins is done by vision.
 Improvements:1. Using a Perspex glass with a bigger height. 2. The experiment should be repeated being more accurate with vision and calculations
3. Have the protractor exactly on the line.