Objective

The purpose of this experiment is to prove the laws of reflection andrefraction, and to determine the angle of the total internal reflection and the index ofrefraction in the experiment.

Theory

The theory being experimented in this procedure is that of Willebrord Snell.From his theory we understand that the incident ray, the normal line and the refracted ray

all lie on the same plane. We also understand that the relationship is defined in a ratio with the following equation;

Which means that the ratio of the sine of the angle of incidence to the sine of the angle of refraction, I equal to the ratio of the speed of light in the original medium and the speed of light in the refracting medium.

ProcedureWe set up the optics track, light source and the ray table. We then aligned the flat side of the mirror with the ray of light from the light source.We rotated the ray table in increments of 10 ̊. The first set were done going clockwise. Once done we then did the same thing but going counterclockwise. This gave us the Angles of Reflection. FromThe two Angles of Reflection we were able to calculate the average Angles of Reflection, listed in Table 1.

For the Law of Refraction, we replaced the mirror with a Acrylic cylindrical lens. We rotated the ray table clockwise by increments of 10̊ again. We repeated the same measurements but instead with counterclockwise angles. From the two angles of refraction we were able to calculate the average angles of refraction.

Finally, we aligned the flat side of the lens so that incoming light ray struck the cylindrical surface. We rotated the ray table until the refracted ray disappeared completely and only the reflected ray was visible. This is the angle of incidence. This gave us our angle of incidence theoretical value. From this we were also able to calculate the angle of refraction.

Results

Table 1 – The Law of ReflectionAngle of incidence

Angle of reflection(clockwise)

Angle of reflection(counter clockwise)

Average angle of reflection

10 12 8 1120 23 18 20.530 32.5 29 30.7540 42.5 39 40.7550 53 49 5160 63 59.5 61.2570 73.5 69 71.2580 83 79 81A80ngle of

0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

80

90

f(x) = 1.00654761904762 x + 0.642857142857146R² = 0.999932160123091

Series2Linear (Series2)

Slope from graph = 1.0065

Table 2 – The Law of RefractionAngle of incidence

Sin Angle of refraction(clockwise)

Angle of refraction(counter clockwise)

Average angle of refraction

Sin

10 .174 9.5 11 10.25 .17720 .342 20 20.5 20.2 .345

30 .5 30 30.5 30.2 .50340 .643 39.5 41 40.5 .64950 .766 49.5 50.5 51 .77760 .866 59.5 61 60.25 .86870 .94 69.5 71 70.25 .94180 .985 80 80.5 80.2 .985

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.10

0.2

0.4

0.6

0.8

1

1.2

f(x) = 1.0013699119235 x − 0.00452314850484181R² = 0.999862171339181

Series2Linear (Series2)

Slope from graph = 1.0014Index of Refraction n = 1.43

% error n = [(1.0014 – 1.43) / 1.43 ]* 100% = 29.97%

Data Table 3 – Critical AngleCritical Angle = 44.0Angle ofIndex of Refraction = 1.43Nglass = 1.43% error = [ ( 1.43 – 1.43 ) / 1.43 ] * 100% = 0%

Conclusion

The experiment was unsuccessful for our group due to the % error had from data table 2. But we know this was due to inaccurate reading when taking the angles. Otherwise if it had been a lot

more accurate it would have correlated with the theory. A way we can improve future results is by double checking our readings or taking multiple readings.