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# Physics AS Specimen Paper. Wtf do I do. This is scaring tf out of me.

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Why bother with a post grad course - waste of time? 17-10-2016
1. A student has a diffraction grating that is marked 3.5 * 10^3 lines per m.
Calculate the percentage uncertainty in the number of lines per metre suggested by this marking.

FREAKING WOT M8. Okay but on a serious note.. how do I know what the uncertainity. I feel like it has something to do with number of sig figs they give the value to. Pls help.!
2. (100/3.5*10^3)*100
=2.9%
this should be it, check the mark scheme
3. (Original post by cleggj88)
(100/3.5*10^3)*100
=2.9%
this should be it, check the mark scheme
Could you explain it? Why is the uncertainity 100?
Could you explain it? Why is the uncertainity 100?
It rounds to 3.5*10^3, so the true value lies in the interval 3.45*10^3<x<3.55*10^3. Therefore the uncertainty is +-50, =100 total
5. (Original post by samb1234)
It rounds to 3.5*10^3, so the true value lies in the interval 3.45*10^3<x<3.55*10^3. Therefore the uncertainty is +-50, =100 total
Wait so isnt the uncertainty +- 0.05 = 0.1? :/
Wait so isnt the uncertainty +- 0.05 = 0.1? :/
+-0.05*10^3 =50
7. (Original post by samb1234)
+-0.05*10^3 =50
All this for one mark? *cries*
Thanks a bunch!
All this for one mark? *cries*
Thanks a bunch!
no problem, let me know if you have any other issues
9. (Original post by samb1234)
It rounds to 3.5*10^3, so the true value lies in the interval 3.45*10^3<x<3.55*10^3. Therefore the uncertainty is +-50, =100 total
This is right

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