Just took my final but I think there was an invalid question

Discussion in 'Odds & Ends' started by MarinaHighTennis, Dec 7, 2011.

  1. MarinaHighTennis

    MarinaHighTennis Professional

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    Last edited: Dec 7, 2011
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  2. Talker

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    Isn't I( initial ) just set to 100? No matter what it is (I) would be a percentage of that if I'm looking at this right.

    Good luck! :)
     
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  3. MarinaHighTennis

    MarinaHighTennis Professional

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    Sounds logical, I wish our teacher told us that. Brainfuse didn't even know how to do this problem
    I already took my final, but I was stuck on this question. :(
     
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  4. thug the bunny

    thug the bunny Professional

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    MHT, I think you are right, something is wrong with the question.

    Transmittance should be unitless, either as a ratio <1, or as a percentage, not EU (is that Euros?). Absorbance is in units of AU (absorbance units). And, why ask what Io is, when it is always defined as 100%? Doesn't make sense...
     
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  5. MarinaHighTennis

    MarinaHighTennis Professional

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    I hope the teacher didn't screw us over for the final, but EU is energy units so its not really a unit of measurement.
     
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  6. toly

    toly Hall of Fame

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    I’m very sorry, but IMO your answer is not exactly right.

    By definition , see please http://en.wikipedia.org/wiki/Transmittance ,transmittance is

    T=Iout/Iin (1)

    where Iin is the intensity of the incident radiation and Iout is the intensity of radiation coming out of the sample.

    The absorbance is

    A=Log(Iin/Iout) (2)

    We know that Iout = 10 EU and A = 2.
    From (2) we have

    Iin / Iout = 10** A = 10**2=100.

    Thus T = 1/100 =1%

    From (1)
    Iin = Iout*100 = 1000 EU
    :confused:
     
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  7. toly

    toly Hall of Fame

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  8. MarinaHighTennis

    MarinaHighTennis Professional

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    Thanks for the help but one thing that puzzled me is that If A= log(1/T) and T=10 it comes out to be -1. Do we ignore the T=10?
     
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  9. toly

    toly Hall of Fame

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    According to definition T=Iout/Iin.

    Thus, T is always less or equal to 1 (0<T<1).

    In your case: T=0.01=1%, Iout=10 EU, and Iin =1000 EU.

    If T=1/100 than 1/T=100 and A=log(1/T)=log(100)=2.

    EU is complicated energy unit.
     
    Last edited: Dec 8, 2011
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  10. BaboFan

    BaboFan Rookie

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    Correct me if I'm wrong but isn't 2 Max absorbtion? So t is? 0% and I 0
     
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  11. toly

    toly Hall of Fame

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    If (0<T<1) than (∞>1/T>1)

    A=log(1/T)

    If 1/T=1 than A= log(1)=0

    If 1/T=∞ than A=log(∞)=∞

    So, (0<A<∞)

    and Amax=∞
     
    Last edited: Dec 8, 2011
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