# Chemical Forums

## Specialty Chemistry Forums => Nuclear Chemistry and Radiochemistry Forum => Topic started by: MIK90 on June 30, 2020, 06:04:38 AM

Title: CALCULATION HALF LIFE TIME
Post by: MIK90 on June 30, 2020, 06:04:38 AM
Hi

i am beginner in the field of radioactivity and I have a problem to solve , however I would like your help. I have to calculate half life time of element and I have the activity values ( 400,200, 100 MBq)  and time points (5,4,3 min) .I would like to ask you how I can calculate the half life time with these values. should I use the formula A=Ao e-λt   ??
Title: Re: CALCULATION HALF LIFE TIME
Post by: Babcock_Hall on June 30, 2020, 07:49:36 AM
Do you know the meaning of λ in this formula and how it is related to the half-life?
Title: Re: CALCULATION HALF LIFE TIME
Post by: Enthalpy on July 01, 2020, 04:04:53 AM
Is that formula really necessary? Observe the data. 400 - 200 - 100 MBq and 3min - 4min - 5min, does that ring a bell?
Title: Re: CALCULATION HALF LIFE TIME
Post by: pcm81 on May 12, 2021, 12:37:54 PM
I realize that i am about a year late to the party, just want to add some information for anyone that finds this thread in the future.
λ=ln(2)/HL
where λ is the probability of decay per second and HL is half life in seconds.
dN/dt=-λN this basically means the rate of decay is defined by probability of decay times amount of material present.

solution to this equation is exponential.
N(t)=N0*exp(-λt)

in the experiment one measures rate of decay at different time values.
Plot would be a falling exponential.
If one takes natural log of the decay rate the resulting graph is a linear function, the slope of which is λ.
At this point one can calculate half life from λ=ln(2)/HL by solving for HL.