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Homework Help: Snell's law

  1. Oct 28, 2007 #1
    Snell's law[SOLVED]

    1. A ray of light travels from air(which is given to be 1.0003 I also had it be N1) into a liquid. The ray is incident upon the liquid(n2) at an angle of 30 degrees. The angle of refraction is 22 degrees.
    Indices of Refraction.
    Medium. . . .N
    Air.. . . . ....1.0003
    Crown Glass.1.52
    Flint Glass---1.62

    2. n1 X sinO1= n2 X sin02

    3. n1 X sinO1= n2 X sin02 Alright so I am given the O1, O2, N1, but not N2 so I will plug in the numbers.

    1.0003 X sin(30)= N2 X sin(22) Then I continue to do the math
    1.0003 X -0.988031624 = N2 X -0.00885130929
    -0.988328033= N2 x -0.00885130929
    so N2= 111.658965

    My main problem is that the math doesn't any of the mediums we are given. Did I make a mistake in my work or is the book wrong? I have gone over this many times with myself.
    Last edited: Oct 28, 2007
  2. jcsd
  3. Oct 28, 2007 #2


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    Those values for sin look very wrong. You should have memorized the sine of 30 degrees, and should have a rough idea about the sine of 22 degrees, so you should be able to recognize that your calculation is wrong.
  4. Oct 28, 2007 #3
    So then it would become
    1.0003 x .5 (I knew something looked wrong should not use google calculator ever again.)= n2 X 0.374607
    .50015= N2 x 0.374607
    Divide by 0.374607
    N2= 1.33

    Thank you!
  5. Oct 28, 2007 #4


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    Don't forego google calculator, just use it correctly! This is a lesson in always writing your units. :smile:

    Try asking it "sin 30 degrees".

    Without the angle marking, it assumed radians.
  6. Oct 28, 2007 #5
    Oh. Well thank you! Units are very important I just tried google calculator again and wrote radians got the same answer then I did degrees and got .5, Thank you!

    Units are important.
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