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Critical Angle

  1. May 1, 2012 #1
    Snell's Law of Angles says that : sinA/sinB = nB/nA

    but in order to find critical angles B has to be 90° . I understand that in order to have total internal reflection that nB/nA < 1 but why can't there be a CRITICAL angle when nB/nA > 1 ?

    sinA would have to be greater than 1 which cannot happen but if i do it separately : glass to air and water to air and say that air-n-water = nwater/nair it is 1.33/1.5 which is true but if i do it in one go it is 1.5 / 1.33 . I must be doing something wrong , because this seems too easy :S
  2. jcsd
  3. May 1, 2012 #2


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    Staff Emeritus
    Science Advisor

    What do you mean by "if i do it in one go"?
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