The count rate from a radioactive sample falls from 4.0 × 106 per second to 1.0 × 106 per second in 20 hours. What will be the count rate 100 hours after the beginning?
We know that,
Where,
A= Activity of the substance=1 × 106 s-1
A0 = Initial activity=4 × 106 s-1
t = time=20h
λ = decay constant
So according to the problem,
Now we have to evaluate activity after 100 hours
A = 3.9× 103 disintegrations per second
Hence, the activity after 100 hours is 3.9× 103 disintegrations per second.