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    A student has a diffraction grating that is marked 3.5x10^3 per m.

    Calculate the percentage uncertainty in the number of lines per metre suggested by this marking. (1 mark)


    I have seen the mark scheme says it is 2.9%, however i don't know how to get that answer... I got the answer of 0.000029%....
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    (Original post by Smile Generator)
    A student has a diffraction grating that is marked 3.5x10^3 per m.

    Calculate the percentage uncertainty in the number of lines per metre suggested by this marking. (1 mark)


    I have seen the mark scheme says it is 2.9%, however i don't know how to get that answer... I got the answer of 0.000029%....
    Can you post the exact question, and your working out pls?
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    Just from what you have given, i assume that you have
    1) not taken the factor of \times 10^3 into consideration
    2) Not multiplied by 100 to get percentage instead of decimal as
    2.9 \times 10^{-5}=0.000029.

    Besides, what the mark scheme wants is \frac{1}{3.5} it seems.
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    (Original post by Kyx)
    Can you post the exact question, and your working out pls?
    That was the exact question.

    I did (1/3.5x10^3)x100
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    I'm having trouble finding the absolute uncertainty in the number of lines per metre, for 3.5 x 10^3 lines per metre.
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    To get to the answer, you need to do (100 / 3.5 x 10^3) x 100, which gives you an answer of 2.857142%, which rounds to 2.9%
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    Would that not give you per cm though?
 
 
 
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