Experiment 7: Reflection and Refraction

Introduction: The purpose of this experiment is to examine some simple examples of reflection and refraction and relate them to Snell's law

Procedure: We set up a light box with a slit of light pouring out. We then directed that slit at the flat side of an acrylic semicircle. We set the semicircle on a protractor and rotate the entire set up to measure the angle of refracted light coming out the other side. We did this for 10 trials, taking data down starting at 10 degrees and ending on 70 degrees.

 We then attempted to do the same thing on the rounded side of the acrylic semicircle but were forced to stop at 44 degrees, only taking down 8 data sets.

Data:

Flat side of acrylic:

Theta 1 (degrees)	Theta 2 (degrees)
10	7
15	12
20	14
30	20
35	23
40	25
45	30
50	32
60	36
70	41

This is Theta 1 vs. Theta 2

Sin(Theta 1) vs. Sin(Theta 2)

Round side of acrylic:

Theta 1 (degrees)	Theta 2 (degrees)
0	0
5	7
10	15
15	24
20	35
30	53
40	75
44	90

Theta 1 vs. Theta 2

Sin(Theta 1) vs. Sin(Theta 2)

Analysis: We were not able to complete the 10 trials on the round side of the acrylic because we witnessed total internal reflection at 44 degrees. This is the last angel we could muster before total internal reflection.

The equation of the line from the flat side of the acrylic can be rewritten as sin(theta 1)/sin(theta 2)=1.48. Rearranging Snell's law, sin(theta 1)/sin(theta 2)=n two/n one. Therefore, 1.48 equals n of air/n of acrylic, given n one is air in this case. For the rounded side of the acrylic, the equation of the line can be rewritten as sin(theta 1)/sin(theta 2)=0.667. Using the rearranged version of Snell's law, 0.667 equals n of air/n of acrylic, given that n one is acrylic in this case because the light is being refracted after it has already entered the acrylic. Indeed, the second slope is the inverse of the first one.