# Nuclear Decay question without knowing N0 or N ?

1. May 9, 2012

### Bowenwww

Nuclear Decay question without knowing N0 or N ??

1. The problem statement, all variables and given/known data
Ok so what I have an Am sample which emits alpha particles at a rate of 70Bq in 1997 and asks for the activity 8 years later (the half life of Am being 432.2 years) I found this to be 69.108 Bq, first of all does this sound right?

Secondly it asks for the number of nuclei both in 1997 AND 8 years later in 2005 - I have no idea to do this, is there an equation that relates the initial and final nuclei number without knowing either?

2. Relevant equations

3. The attempt at a solution

2. May 9, 2012

### Dickfore

Re: Nuclear Decay question without knowing N0 or N ??

$$A(t) = A_0 \, \exp(-\lambda \, t)$$

A is activity and is measured in bequerel ($1 \, \mathrm{Bq} = 1 \, \mathrm{s}^{-1}$)

3. May 9, 2012

### daveb

Re: Nuclear Decay question without knowing N0 or N ??

Also, A(t) = λN(t)

4. May 9, 2012

### Bowenwww

Re: Nuclear Decay question without knowing N0 or N ??

Yeah I sort of understand that it's just I don't know how to apply my answer for activity to find the nuclei number before and after

5. May 9, 2012

### Dickfore

Re: Nuclear Decay question without knowing N0 or N ??

see post #3.

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