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Can someone see if this is the right way to do? First time taking physics

  1. Aug 1, 2012 #1
    1. The problem statement, all variables and given/known data
    1. If v is constant, how does f change if λ quadruples?
    2. c is equal to 3x10^8 m/s. What is the value of n if v equals 2.25 x 10^8 m/s
    3. If n2 is greater than n1, is Ө1 greater than, less than, or equal to Ө2? Prove using third equation.
    4. Assuming Ө2 is 90 degrees, write an expression for Ө1 in terms of n1 and n2.


    2. Relevant equations
    v=λf
    n=c/v
    n1sinӨ1=n2sinӨ2


    3. The attempt at a solution
    1. First one I plug in random number leaving the constant the same for both, and using 1 for initial equation and 4 for quadruple second equation. Thus, I got 20 first time and 5 second. time SO it GOT SMALLER
    2. 3x10^8/2.25x10^8 = N=4/3
    3. I have no clue, I plug in 4 for n2 and 2 for n1. Rather or not theta was bigger was confusing....
    4. I got sin theta1= n2*sin90/n1.....
     
  2. jcsd
  3. Aug 2, 2012 #2

    PeterO

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    Homework Helper

    The third formula says:

    n1sinӨ1 = n2sinӨ2

    Since the product n.sinθ is a constant, if n becomes larger, sinθ must become smaller. Since the angles here have 0 ≤ θ ≤ 90, if sinθ is smaller, then θ is smaller.
    SO if n2 > n1 then Ө2 < Ө1

    For part 4. don't forget that we know the exact value for sin90.
     
  4. Aug 2, 2012 #3
    They probably want you to be more specific, and say that it got smaller by a factor of 4.
     
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