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Angle of Incidence vs. Angle of Refraction

October 23, 2011 by alison12 · No Comments · Uncategorized

Angle of Incidence vs. Angle of Refraction

Background Information:

Light is a form of energy which allows us to see by the light entering the eyes and forming an image. Light can be absorbed, reflected and refracted. When the speed of the light changes after hitting a surface of a difficult optical density, making it look as if it is bending, this is called refraction. Some surfaces that refract light include air, water, glass, diamond and Perspex.

Aim:

To investigate what the relationship is between the angle of incidence and the angle of refraction.

Hypothesis:

The greater the angle of incidence, the greater the angle of refraction will be.

Materials:

  • One A4 sheet of paper
  • Two protractors
  • One transparent semi-circle prism
  • One light box kit
  • Power supply

 

Safety:

Be careful when touching the hot light box, as it could burn.

Do not stick anything inside the power supply.

There is no safety equipment required.

Variables:

Independent Variable: The angle of incidence

Dependent Variable: The angle of refraction and the angle of bending

Controlled Variable: The transparent shape

Method:

  1. Set up the light box, paper and semi-circular prism.
  2. Draw on the paper the normal and boundary line. This step is optional, but recommended to increase accuracy.
  3. Have the angle of incidence start at 40o. Measure the angle of refraction and the angle of bend.
  4. Complete step 3, each time increasing the angle of incidence by 10o.

 Science Focus 4

 Results:

Angle of Incidence

Angle of Refraction

Angle of Bending

1st Attempt 2nd Attempt 1st Attempt 2nd Attempt
40o 30o 29o 10o 11o
50o 32o 31o 18o 19o
60o 34o 33o 26o 27o
70o 36o 35o 34o 35o
80o 38o 37o 42o 43o
90o 40o 39o 50o 51o
100o 42o 41o 58o 59o


 

 

 

 

 

Discussion:

The first trend noticed was the fact that the angle of refraction and the angle of which it bends added together equalled the angle of incidence. The material with the higher refractive index causes the light to slow down because the light hits the surface on an angle, the rays of light contact the Perspex at different times, and therefore, slow down at different times. This gives the appearance that the light bends in the Perspex. The angle of bending is the difference between the angle of incidence and the angle of refraction.

The second trend is the results collected for the angle of refraction always increases by two degrees as the angle of incidence increases by ten degrees. This occurs because the material (Perspex), the position of the material and the direction at which the light beam comes from are never changed. This makes for a fair experiment, which is why the angle of refraction always increases by two degrees.

Evaluation

The data was collected twice in this experiment. This is in order to make sure the experiment is fair and see if the results are accurate. The results were accurate. This is shown because both sets of results were extremely similar to each other, only differing by one degrees. The reason for this difference is both attempts were done on different days, and when the second attempt was completed, the position of the Perspex and the directed of the light beam were most likely changed slightly from the first attempt.

One benefit of the experimental design was keeping the same material for the light beam to pass through. If it had changed, the results wouldl have been innacurate. Another strength was drawing on paper the normal. Doing so made it easier to calculate the angle of incidence and the angle of refraction.

The first improvement that could have been made is keeping the light box in the exact same place in the second attempt as it was in the first attempt, the reason being the different results in the two experiments. The second improvement that could have been made in order to increase accuracy of the results was the fact that it was rushed. The group didn’t have much time to do the experiment because of confusion about the task, and a lot of time was wasted trying to decide on an experiment, hence the rushed manor in which the task was completed.

The method allowed me to collect relevent data to test and confirm the hypothesis: the greater the angle of incidence, the greater the angle of refraction will be. The method was good because it was simple and easy to follow without major error. However, the simplicity of the method is also a thing that could be improved on because it could become quite boring and repetitive using such a simple method.

If furthur investigation were to take place, it would have been interesting to test what happens to the relationship between the angle of incidence and the angle of refration when the direction of the light beams compared to the normal is changed significantly. It would also be interesting to use different substances for the light to pass through instead of Perspex, such as plastic or glass.

Conclusion

The hypothesis, the greater the angle of incidence, the greater the angle of refraction will be, was supported. The relationship between the angle of incidence and the angle of refraction is that the angle of refraction increased as the angle of incidence did.

 

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