SCN Unit 2 Physics Name:__________________ Date:___________
Purpose: To explore the path of light as it travels from one transparent medium to another.
Materials: Ray box with single slit
Procedure:
Semicircular acrylic block Polar graph paper
1.
Using the polar graph paper, place the acrylic block at the centre of the paper with its flat edge along the horizontal centre line. The normal will be the vertical line going through the centre of the acrylic block.
2.
Project a single ray of light at the centre of the flat edge of the block at an angle of incidence of 0° (along the normal). Measure the refracted ray and record in your observations
3.
Repeat step 2 for the remaining angle sin your chart. Remember to measure your angle of refraction with respect to the normal. At some point you may notice a reflected ray coming back into the air. Ignore this for now. We will return to the reflected ray later on.
Observations:
Angle of incidence in
Air (< i)
0°
10°
20°
30°
40°
50°
60°
Analysis:
1
Angle of refracted ray in acrylic block
(<R)
0°
5°
13°
19°
25°
30°
35°
< 𝑖
< 𝑅
0
2.000
1.538
1.578
1.600
1.667
1.714
0
SIN< i
0.17364
0.34202
0.50000
0.64278
0.76604
0.86602
0
SIN < R
0.08715
0.22495
0.32556
0.42261
0.50000
0.57357
0
𝑆𝐼𝑁 < 𝑖
𝑆𝐼𝑁 < 𝑅
1.992
1.520
1.536
1.521
1.532
1.510
What was the angle of the refracted ray in acrylic for the initial angle in air of 0°? Does this answer make sense to you? Explain.
The angle for the refracted ray for the initial angle of 0 degrees was also 0 degrees. Yes this makes sense because if you shine a light ray perpendicular to the surface of a second medium, you don’t get any refraction. This is because the whole light beam is being slowed down at the same rate. You only get refracted rays when hitting a second medium at an angle. This causes the closer edge of the beam of light to slow down more quickly than the far edge of the beam, causing the light to bend. (Refer to the example of the wagon going from pavement to sand on an angle)
2
3
How did the value of the angle in air (angle of incidence) compare with the angle in acrylic for the remaining measurements?
The angle in air was always larger than the angle in the acrylic meaning the refracted ray bent towards the normal. This is because light travels slower in the acrylic because it is more dense then air (particles are closer together).
Which way did the refracted ray in the acrylic bend when compared to the normal?

SCN Unit 2 Physics Name:__________________ Date:___________
A slower medium causes light to refract and the angle with respect to the normal with decrease.
Therefore the angle of incidence (faster medium) was larger than the angle of reflection (slower medium). In other words, light will bend towards the normal when it is slowed down, and away from the normal when light speeds up.
4
5
With the exception of the first measurement, what did you notices about the ratio
<𝑖
<𝑅
?
The ratio was somewhere between 1.5 and 2, but the measurement for the angle of incidence of 10 degrees seemed a bit off and didn’t quite follow the data either.
𝑆𝐼𝑁<𝑖
Again, with the exception of the first measurement, what did you notices about the ratio
𝑆𝐼𝑁<𝑅
?
The ratio of the SIN of the angles seemed to be around 1.5 indicating that the index of refraction for acrylic is close to 1.5.
6 Which ratio (from Q 4 and 5) is nearly constant?
The ratio in Q5 seemed to be almost constant.
7 Why do you think you used a semi-circular medium in this experiment? How would things change if you used a rectangular shaped medium?
This is so that the light was only refracted once. If you had a rectangular piece, light would be refracted when going from the air to the acrylic, and then refracted again when it went from the acrylic back to the air. This is because each time the light hit a new medium; it would be hitting the new medium at an angle which would cause refraction to occur. IT would be hard to get accurate results to use to compute the index of refraction if the light is refracted twice. The semicircular piece of acrylic eliminates this problem. The light is refracted when it goes from air to acrylic but does not refract when it goes from the acrylic to air because the edge of the acrylic is curved at this edge allowing the light beam to hit the edge at 90 degrees and therefore eliminating the second refraction. (when light hits a surface at 90 degrees it does not refract it travels straight through, see Q1.)
Conclusion: Light will bend (refract) when it enters a new medium. It will bend towards the normal if entering a slower medium and away from the normal for a faster medium.