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Light - Angle of Deviation and Lenses

  1. Mar 8, 2008 #1
    Hey guys, i have two question that me and a couple of my mates couldn't figure out for the life of us in class so i bring them here. The first one at first glance seemed fairly easy

    1. The problem statement, all variables and given/known data

    Calculate the angle of deviation at a glass air interface for an angle of incidence of 65 degrees and refractive index of glass at 1.55

    2. Relevant equations

    n1 * sin ( incidence angle ) = n2 * sin ( refractive angle )

    3. The attempt at a solution

    1.55 * sin (65 ) = 1 * sin(x)

    1.40 = sin(x)

    sin-1(1.40) = x

    BUT WAIT you cant do sin inverse of a number higher than 1 so can some one please help me

    The Second problem we didn't have the slightest clue as to where to start.

    2.Use the ray tracing or the formula method to determine the magnification of an object placed under the following two-lens microscope. The object is placed 5.2mm from an objective lens of focal length 5.0mm.They eye-piece lens has a focal length of 40mm. The poles of the lenses are 150mm apart.

    Please Help Thanks Sinners
  2. jcsd
  3. Mar 8, 2008 #2


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    Are you going from air to glass or from glass to air? You may have n1 and n2 flipped around. If it's glass to air, then you may be dealing with total internal reflection and there is no emerging beam.
  4. Mar 8, 2008 #3
    well in the text book it says from a glass-air interface so i assumed it was from glass to air.
  5. Mar 9, 2008 #4
    sorry to bump but this is due tomorrow

    thanks sinners
  6. Mar 9, 2008 #5


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    As you've said, there is no solution glass to air. Try air to glass. What are you asking about?
  7. Mar 9, 2008 #6
    i tried air to glass and got an angle of deviation to be 30 degrees however in the book the answer is 19 degrees. Also any help on the second question?
  8. Mar 9, 2008 #7


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    I get the angle of refraction to be ~35.8 degrees. Is that what you got? But now it's semantics. They didn't ask for the angle of refraction, they asked for the angle of deviation. I would call that 65-35.8. But that gives me about 29.2. So if the book answer is 19, I don't know. Second one, don't know. I've always hated lens problems, sorry.
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