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Homework Help: Refractive Index

  1. Dec 29, 2011 #1
    Part A i just need to know if i have done it properly.
    Part B is done
    Part c dont have a clue :cry:

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


    2. Relevant equations
    Law of refraction n1*sinχ1=n2*sinχ2
    Critical Angle sine(x) = nr/ni

    3. The attempt at a solution

    part a is on the image above

    part b I have done it

    Part c no idea
  2. jcsd
  3. Dec 29, 2011 #2
    Read the wording of the question very carefully.....the ray is totally internally reflected at P for the first time.....
    This means that the ray is striking the surface at the critical angle..... can you see which angle is the critical angle??
  4. Dec 29, 2011 #3
    Part A All OK.
    Part B apply snells law you have all the info!

    Part C I have looked at the question paper on the the AQA website and part c is worth 1mark! This means no formula are needed!
    The important line is "At this point the angle of relfection is 27 and the ray is totally internally reflected for the first time."
  5. Dec 29, 2011 #4


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    And technician directly addressed that issue.

    Another way to look at this is that the critical angle is angle of incidence for which the angle of refraction would be 90° .

    I hope that helps.
  6. Dec 29, 2011 #5
    Thanks guys I just reliased I was being stupid. I was taking the angle of incident for the critical angle to be 27° instead of taking it from the normal. Thanks for the help:tongue:
  7. Dec 30, 2011 #6
    I was writing this as technician was writing. He pressed submit before I did thats all!
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