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    hi i have been given the following question but i am unsure about what i should do
    1) calculate the effective speed of light in
    a) a fibre optic glass of refractive index n=1.58
    b) fibre optic cladding of refractive index n=1.56

    could any1 please explain to my step by step how i would go about answering this question?

    thanks
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    anyone?
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    Ok do you know any equations you can use involving a refractive index?
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    is this one n=sini/sinr
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    Does this sound familiar?
    _{1}n_{2} = \frac{c_{1}}{c_{2}}
    where _{1}n_{2} is the refractive index from medium 1 (here it should be a vacuum) to medium 2 (the glass) and \frac{c_{1}}{c_{2}} is the speed of light in medium 1 (the vacuum) divided by the speed of light in medium 2 (the glass)?
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    so do you know for q1 part a would the answer be 1.58=speed of light in air/ speed of light in optic glass?
    1.58=3*10^8/?
    ?=3*10^8/1.58
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    That sounds about right...
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    i get this on calculator 189873417.7 would i round this to 1.89*10^8
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    i am unsure about question 1 part b
    do i do the same as in q 1a or do i need to divide the refractive index by something first?
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    (Original post by panjabiflower)
    i get this on calculator 189873417.7 would i round this to 1.89*10^8
    if you're doing that, at least round it properly to 1.90*10^8
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    (Original post by alex-hs)
    if you're doing that, at least round it properly to 1.90*10^8
    oh yh stupid mistake - have you got any idea about what i do for question 1 part b?
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    (Original post by panjabiflower)
    oh yh stupid mistake - have you got any idea about what i do for question 1 part b?
    the same as you did for part a, but with the other value for the refractive index. Or am I missing something :confused:
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    In question 1b you do the same thing as in 1a - speed of light in air and in the new glass instead of the old one... Basically just replace 1.58 with 1.56...
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    Formula to use is: \displaystyle v = \frac{c}{n}

    v - velocity of light in medium
    c - velocity of light in vacuum
    n - refractive index of medium
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    so is answer for part b) 1.92*10^8
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    Yup!
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    does any1 know any equations to work out critical angles?
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    HINT: what's the angle of refraction at the critical angle?
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    is it 90 degrees
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    yup - so sin r = ?

    EDIT: And then plug into n = sin i/sin r
 
 
 
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