Question

a sample of f-18 is used internally as a medical diagnostic tool to look for the effect of the positron decay T/2 =110min
how long does it take for 99% of F18 decay ?
​

Answer 1

Answer:

Explanation:

From law of radio activity,N=N  

0

​

e  

−λt

 

Here decay constant, λ=  

t  

1/2

​

 

0.693

​

=0.693/110=0.0063min  

−1

 

Let, N  

0

​

=100 so rest amount after decay at t N=(100−99)=1

So, 1=100e  

−(0.0063)t

 

or e  

0.0063t

=100 or 0.0063t=ln100=ln10  

2

=2ln10

or t=730 min

Answer 2

Answer: t= 731 min

Explanation: