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Homework Help: Angle of light question

  1. Nov 22, 2007 #1
    I have a example where a light goes into a triangular glass from air. I used the protractor to calculate the angle of incidence. I then used that angle and plotted in an equation to find the angle of refraction and then drew the refracted ray. So by now the light should exit the glass and enter air.

    I did the exact same thing as I did with the angle of incidence, except when i try to calculate the angle of refraction I get an error on my calculator. In this situation, what am i suppose to do?

    if im not clear enough please tell me.
  2. jcsd
  3. Nov 22, 2007 #2


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    You are not clear enough....
    But I can guess that your error is probably from attempting an inverse sine of a number larger than 1. Said number being the index of refraction times the sine of the other angle. This would indicate that you were...
    a.) Solving for the angle for the light in air given the light in the medium with higher index of refraction...
    b.) Starting with an angle inside the refractive medium which is too large to refract and rather will exhibit total internal reflection.

    If a.) was not your intent then double check your use of the refraction formula (Snell's/Descartes' law) you likely have your angles reversed.
  4. Nov 23, 2007 #3


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    You have found the angle of incidence and angle of refration on one face of the prism. Measure the angle of incidence inside the glass on the second face. Refractive index of the glass* angle of incidence in the glass = Angle of refraction in the air*Refractive index of air, which is one. Now find the angle of refraction
  5. Nov 23, 2007 #4


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    Maybe you should show us your calculations in more detail.
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