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PLEASE PLEASE HELP - Qu on Light refraction

  1. Mar 24, 2006 #1
    A block of crown glass (refractive index - 1.52) is covered by a sheet of water (refractive index - 1.33). a ray of light incident on the water with a angle of incidence of 55 degrees. find the angle that this ray makes with the normal when it emerges from the glass.........

    PLEASE help, this is the only question i cant do...


    Regards Ryan Voy

  2. jcsd
  3. Mar 24, 2006 #2


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    HINT: Apply Snell's Law at each of the three interfaces.
  4. Mar 24, 2006 #3
    thanks i knew i had to do that but im getting a different answer to the text book,

    My answer - 32.61 degrees'

    text books answer 69.4 degrees

    sorry 4 the trouble

    Thanks regards Ryan

  5. Mar 24, 2006 #4


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    The answer should be exactly 55 degrees, and you can do this without even invoking Snell's law explicitly. As long as the sides of all the interfaces are perfectly parallel, the exit ray in the same medium has to be parallel to the incident ray in that medium.

    EDIT : This is assuming that the glass is covered on only one side with water and the final ray emerges into air.
  6. Mar 25, 2006 #5
    :smile: Thanks i will check Monday with the teacher, hopfully its right :smile:

    Regards Ryan,

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