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Homework Help: NA of fibre immersed in water?

  1. Mar 4, 2010 #1
    1. What will the NA of the fibre be if it's immersed in water?
    Basically we know the NA = 0.30 and refractive index is 1.50 for the fibre's core.

    2. Snell's law

    3. My theory is that NA is the sine of the critical angle.
    n1 = 1.5, n2 = 1.333
    NA = sin (theta_crit) = sin (arcsin (n2/n1)) = n2/n1 = 0.89

    But our teacher said it was not correct but on the right track. Is there a possibility that the NA doesn't even
    change when the fibre is immersed in water?

  2. jcsd
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