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Homework Help: Snells law

  1. Mar 16, 2005 #1
    so my given is 1.52 20degrees = 1.10 sin r

    im trying to find sin r which comes out to 18.9 degrees but im not sure how find that, can somebody help me out please?

    so you do 1.10/1.52

    do you divide that into sin 20?
     
    Last edited: Mar 16, 2005
  2. jcsd
  3. Mar 16, 2005 #2
    I don't quite understand your notation....

    Is that first part : 1.52 * 20 deg?
     
  4. Mar 16, 2005 #3
    snells law is n1 sin i = n2 sin r

    n1= 1.52
    sin i = 20 deg

    n2 = 1.10

    sin r = ?

    sin r actually equals 28.2 deg but i don't understand the process
     
  5. Mar 16, 2005 #4
    Isn't this just simple algebra? What do you get when you solve for the unknown variable?
     
  6. Mar 16, 2005 #5
    I got 27.6 as my answer...
     
  7. Mar 16, 2005 #6
    .........

    [tex]\sin{x}[/tex] does not give you an answer in degrees.

    [tex]n_1 \sin{\theta_1} = n_2 \sin{\theta_2} \Longrightarrow \theta_1 = \sin^{-1}\left( \frac{n_2}{n_1} \sin{\theta_2}\right)[/tex]
     
  8. Mar 16, 2005 #7
    Isn't the question what is sin r? Not what is the angle...
     
  9. Mar 16, 2005 #8
    Well, in that case he's in for a surprise if he wants it to "come out to [tex]18.9^\circ[/tex]"
     
  10. Mar 16, 2005 #9
    but how do you do it

    1.10/1.52 =.723

    sin 20=.723

    then im stuck....
     
  11. Mar 16, 2005 #10
    Look for the [tex] \sin^{-1}[/tex] button on your calculator. Apply it as in the equation I put above.
     
  12. Mar 17, 2005 #11
    first calculate sin(20)
    then multiply that by 1.52
    then divide by 1.10
    then take the arcsin/inverse sin of that number
    make sure its in degrees and yorue done.

    28.2
     
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