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Is Snell's Law valid even when incident ray is Normal to the surface?

  1. May 10, 2012 #1
    According to the Snell's Law refractive index n21= sin i/sin r, but when we use this equation while having a incident light normal to the surface of lens or any other refracting surface it becomes 0/0. So how can we define Snell's law in this situation?
  2. jcsd
  3. May 10, 2012 #2
    [tex]n_1sin\theta_1 = n_2sin\theta_2[/tex]

    This is the actual Snell's law. When you shift the sin over to the other side, you assume it's not 0.
  4. May 10, 2012 #3
    Which one is the actual n21=sin i /sin r or n1 sin i= n2 sin r?
  5. May 10, 2012 #4
    As I said above...

    [tex]n_1sin(i) = n_2sin(r)[/tex]

    The other one is not valid when sin(r) is equal to zero.
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