# HL Nuclear Physics Question

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The half life of an unstable element is 12 days. Find the activity of a given sample of this element after 20 days if the initial activity was 3,5 MBq.

HELP

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To find the amount of something remaining, you use N=No(1/2)t/t1/2

It's really similar to the interest formula you'd use in math. A=P(1+rt)nt or something like that...

Anyways, use the first formula, but instead of saying N, say A for activity. Final activity = (3.5MBq)(1/2)20/12 = 1.1MBq, if I entered that in my calc correctly. In this case, you just had to know the formula, right?

##### Share on other sites

To find the amount of something remaining, you use N=No(1/2)t/t1/2

It's really similar to the interest formula you'd use in math. A=P(1+rt)nt or something like that...

Anyways, use the first formula, but instead of saying N, say A for activity. Final activity = (3.5MBq)(1/2)20/12 = 1.1MBq, if I entered that in my calc correctly. In this case, you just had to know the formula, right?

Yeah. If this comes up on the exam, just remember to use your data booklet yee

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