Question

The activity of a radioactive sample falls from 700s−1 to 500s−1 in 30 minutes. Its half life is close to 

Answer 1

Answer:

From equation of radioactivity we know At = A0 e-λt Where At = Amount of material at time 't' A0 = Amount of substance at t = 0 λ = decay constant ...

Answer 2

The half life of the radioactive sample is t^(1/2) = 142.39 minutes

Explanation:

A = A0 e^(-M)

500 s^(-1) = (700 s^(-1) e^(-M)

e^(-M) = 5/7

λt = ln (5/7)

Or

λ = ln (5/7)  / t = ln (7/5) / 30 min

The half life is t^(1/2) = ln 2 / λ

t^(1/2) = ln (2) / ln (7/5) x 30 min

t^(1/2) = 142.39 minutes

So

the half life of the radioactive sample is t^(1/2) = 142.39 minutes