1. Apr 12, 2010

### ibysaiyan

1. The problem statement, all variables and given/known data

Hi,
The question itself doesnt sound too complicated i some-how got the asnwer,just wondering if its correct or not.

Question is:A radioactuve isotope wuith a half-life of 1.6x10^5 s disintegrates to form a stable product.A pure sample of 'x' is prepared with an initial activity of 25000Bq.
Caclulate the activity of the sample after week one.
2. Relevant equations
A= Ao e^-lamdba (t)
T(1/2)= Ln2 /lamda.

3. The attempt at a solution
I used initial activity as 25k bq now i thought activity to be in /s? i dont know here is what i've done.
A= Ao e^-lamdba (t)
LnA = LnA0 - (lamda)x T
LnA = ln(25000)-(4.33x10^-6 x 604.8x10^3)
A = 1822. <--- would the units be in s^-1?

Again thanks for your input =}.

2. Apr 12, 2010

### Rajini

why dont you use latex for equation..it will be easier to read latex equations..just you use tex tags before and after equations..Also use a single equation instead of multiple equations for e.g.,
$$A=A_0\exp\left(\frac{-t\ln2}{T_{1/2}}\right)$$
Bq is SI unit for radioactivity. i.e. disintegrations per second..or it just same..Bq is same as per second or s-1.
here t = 1 week.

Last edited: Apr 12, 2010
3. Apr 12, 2010

### ibysaiyan

Ah you see i am not familiar with latex usage. I know how useful it is to both OP and thread posters. Anyhow it seems that its correct?Thanks a zillion for your reply!.Thing is i got 14 exams in under 60 days and i am after A* grade i love astrophysics! So i need to get those grades! Sorry went kinda offtopic.I will be posting more questions later these were pretty basic given off by my teacher today.Just trying to be extra-cautious.
ibysaiyan/

4. Apr 12, 2010

### Rajini

I think the equations you write..for eg., in your 1st eqn.
you just need to use tex before and /tex after the eqn. inside [ ] that is enough..for lambda use '\' before it..