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Total Internal Reflection

  1. Apr 29, 2007 #1
    As the angle of incidence increases, the angle of refraction becomes larger.

    Should the underlined word be decreases? why? I think I've found a mistake in the book because according to snell's law of refraction n1sin(theta)1=n2 sin(theta)2 right? If n1>n2 then (theta)1<(theta)2

    Wait, I don't know now. I think I'm getting mixed up with angles and indices. =[ Help please.
  2. jcsd
  3. Apr 29, 2007 #2
    Is there any easy way to remember the relation of n=c/v, snails law, and how the refracted angle behaves when n1>n2 or vice versa?
  4. Apr 29, 2007 #3
    Also, how come the frequency of light doesn't change as is passes from one medium to another? How do you know if the speed of the wave, frequency, or wavelength changes? I know that the speed of sound/light changes when it goes through another medium but how do you know if frequency or wavelength change or stays constant? Is there a rule for this concept? Thanks
  5. Apr 30, 2007 #4
    bump. help anyone please?
  6. Apr 30, 2007 #5


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    The book is correct. The angle of the refracted ray will bend away from the normal for increasing values of incident angle, in both cases of n1>n2 and n1<n2. Perhaps work out a table of values to see for yourself.
  7. Apr 30, 2007 #6


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    I will try to explain this, as I learned it. Maybe someone can fill it in a bit.
    If you think of the wave fronts being parallel to the boundary between the two media, the number of wave fronts (so frequency) passing a point in medium 1 must be the same as the number of wave fronts passing a point in medium 2. If this were not true, wave fronts would be piling up or being destroyed or whatever and there is no physical mechanism for that to happen. So since the speed changes, the wavelength must change, to keep the relation of velocity = frequency*wavelength valid (in both media).

    Hopefully that helps a bit.
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