The purpose of this experiment is to examine the reflection and refraction of the light. By using the light ray traveling through the semicircle plastic, students will collect data of the light's refraction. Once data are collected, the graph of the refraction's angles will be plotted. Using the the logger-pro program to get the trend line of the plot. The slope of the plot is the plastic's index of refraction.
Procedure:
1. Obtain a light box, semicircle plastic, a circular protractor and the Pasco optical kit.
2. Set the light ray traveling in the plastic that starts at the mid-point of the flat side of the semicircle.
3. Answer the questions in the lab manual before get started.
a. What is the angle of the incidence for the light ray at the flat surface? - answer is 0 degree
b. What is the angle of the refraction at the flat surface? - answer is 0 degree
c.What will happen to the light ray as it leaves the plastic piece at the curved edge and goes into air? - Answer is the light will go straight into air. Because the light ray is a straight light, it will be a straight light when it comes out.
d. will this experiment be a situation where light travels from a material of greater density to one of lower density or from lower density to higher density? - Answer is this experiment is a situation of the light travels from the lower density to higher density.
3.Now turn on the light and see if the predicted answers are correct. - yes, they are.
4. Collecting data, the angle of incident is Theta 1, and the angle of the refraction is Theta 2.
|
Trial
|
Theta 1
|
Theta 2
|
Sin (theta1)
|
sin (theta2)
|
|
1
|
0
|
0
|
0
|
0
|
|
2
|
5±0.5
|
2±0.5
|
0.087153179
|
0.03489847
|
|
3
|
10±0.5
|
7±0.5
|
0.173643108
|
0.12186577
|
|
4
|
15±0.5
|
11.5±0.5
|
0.258811587
|
0.19936213
|
|
5
|
20±0.5
|
15±0.5
|
0.342010469
|
0.25881159
|
|
6
|
25±0.5
|
18±0.5
|
0.422606599
|
0.30900818
|
|
7
|
30±0.5
|
21±0.5
|
0.499986627
|
0.35835786
|
|
8
|
40±0.5
|
26±0.5
|
0.642771837
|
0.43835912
|
|
9
|
50±0.5
|
31±0.5
|
0.766027899
|
0.5150244
|
|
10
|
60±0.5
|
36±0.5
|
0.866009961
|
0.58777026
|
|
11
|
70±0.5
|
41±0.5
|
0.939680297
|
0.6560431
|
5. Plot the graph of Theta 1 and Theta 2.
6. Plot the graph of Sin(theta1) vs. Sin(theta2).
The straight light equation: y = 1.453x - 0.005683.
Slope is equal to sin(theta2) / sin(theta1) = 1.453
7. Set up the new arrangement of the equipment.
a. What will happen to the light ray when it first curved surface of the semicircle pirsm when it is in the position shown? - answer is the light ray goes through the plastic as a straight light.
b. The reason is the angle of incident is zero, so the angle of refraction is also zero.
c. The light ray will come out the flat surface and make the refraction when it goes into air.
d. The experiment will be a situation where the light travels from the higher density to lower density.
9. Rotate the protractor and prism, start collecting data.
|
Trial
|
Theta 1
|
Theta 2
|
Sin (Theta1)
|
Sin (Theta2)
|
|
1
|
0
|
0
|
0
|
0
|
|
2
|
5±0.5
|
4±0.5
|
0.08715318
|
0.06975442
|
|
3
|
10±0.5
|
12.5±0.5
|
0.17364311
|
0.216433332
|
|
4
|
15±0.5
|
20±0.5
|
0.25881159
|
0.342010469
|
|
5
|
20±0.5
|
27±0.5
|
0.34201047
|
0.453978116
|
|
6
|
25±0.5
|
39±0.5
|
0.4226066
|
0.62930479
|
|
7
|
30±0.5
|
52±0.5
|
0.49998663
|
0.787994274
|
|
8
|
40±0.5
|
84±0.5
|
0.64277184
|
0.994517375
|
|
9
|
42±0.5
|
90
|
0.7660279
|
0.999999999
|
|
10
|
60±0.5
|
90
|
0.86600996
|
0.999999999
|
|
11
|
70±0.5
|
90
|
0.9396803
|
0.999999999
|
10. We were no able to complete 10 trials because the refraction disappears (at 90 degree) when the incident ray is at 42 degree.
11. Plot the graph sin(theta1) vs. sin(theta2).
The slope represents the ratio of the plastic's index infraction and air's index infraction.
The equation of the straight line is y = 0.5823x + 0.0548.
This is not the same equation on the earlier experiment.
Summary:
According to the purpose of this experiment, we are going to study the reflection and refraction of the light ray through different density. As the results, the light ray is changing angle differently when it goes through different density. It means that the angle of the refraction depends on the index refraction. The ratio between Sin angle of the incident and sin angle of the refraction is inversely proportional to the ratio between index refraction of two materials.
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