The Refraction of Light Lab
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Introduction
Sasha Zouev. Lab partner Carric Morris
Physics IB, 09.12.05
The Refraction of Light Lab
Aim:
To establish the relationship between the angle of incidence and the angle of refraction when light passes from one medium to the other.
Hypothesis:
From our previous physics classes, we learned that the relationship between the angle of incidence i and the angle of refraction R was
Sin i = λ1 = v1
Sin R = λ2 = v2
From this we can also say that the ratio sin i / sin R should also remain constant, independent of the i value.
Furthermore we are also aware of another relationship which links the angles of incidence and refraction to the refractive index of the substance used. The index of refraction is defined as the speed of light in vacuum divided by the speed of light in the medium. This relationship is called ‘Snell’s law’.
The law is defined as:
Some representative refractive indices. www.wikipedia.org | |
Material | n at λ=589.3 nm |
Vacuum | 1 (exactly) |
Helium | 1.000036 |
liquid water (20°C) | 1.333 |
ethanol | 1.36 |
glass (typical) | 1.5 to 1.9 |
diamond | 2.419 |
n1 sinλ1 = n2 sinλ2
Where n is the refractive index and λ the corresponding angle.
Middle
Table 1. Light going from air into water
Trial # | angle of incidence (i) | angle of refraction (R) | Sin ( i ) | Sin ( R ) | Sin i / sin R (units) |
1 | 20.5 ° | 15.0 ° | .350 | .259 | 1.35 |
2 | 32.0 ° | 23.5 ° | .529 | .390 | 1.33 |
3 | 40.0 ° | 29.0 ° | .643 | .485 | 1.32 |
4 | 51.0 ° | 36.0 ° | .777 | .588 | 1.32 |
5 | 67.0 ° | 44.0 ° | .921 | .695 | 1.35 |
6 | 80.0 ° | 48.0 ° | .985 | .743 | 1.33 |
Average sin i / sin R = | 1.34 | ||||
Data Analysis:
The results we obtained show that on average, we calculated a sin i over sin R to be 1.34 units. Also we can say
Conclusion
Sources of error could have appeared when fiddling with the pins and the lamp during the experimental procedure. The thickness of the ray was not ideal and at times too fat to shine onto one single pin. Also after the ray was refracted, the brightness of the light ray was significantly duller and often very hard to find and trace.
Suggested improvements to the experimental procedure include perhaps using a stronger beam of light (maybe laser) so as to better see the angle of refraction. Likewise, the room in which the experiment is being carried out could be also darker. Further investigations could include observing other mediums. Although in my lab group, we chose to work with water, others were investigating glass, plastic and various oils – all of which would give different data and results.
This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.
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