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Waves percentage uncertainty question

How is the answer 2.9%? Or what is the method to doing this?Screenshot 2024-05-01 at 20.18.03.png
(edited 9 months ago)
Reply 1
I think you do (0.1 / 3.5) * 100 and round to 2sf as the numbers in the question are also to 2sf.
This is because the lines per metre being to 2sf suggests that the measurements can only be made to the closest 0.1. Therefore, the uncertainty is +-0.05 (half the smallest scale division). However, this measurement will have been made on two ends (like how when you measure something with a ruler you measure the start and end) so it's +-0.1 as the absolute uncertainty. You then calculate percentage uncertainty from that.
Don't know if that makes sense, but it seems like a weird exam question to be honest.
Yh makes sense. It's an old spec question

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