VectorHard
Question
The activity of radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes, the decay constant is approximately
Options
A.0.922 per minute
B.0.270 per minute
C.0.461 per minute
D.0.39 per minute
Solution
We know that 
= λN
Now
= λN0; 
- λNt
9750 = λN0; 975 = λNt
⇒ N0 = 10Nt
we know that Nt = N0 = e-λt
= e-λt ⇒ 
= e-λ5
10-1 = e-5λ
Taking log on both sides,
1 - = - 5λ ×
λ =
× 2.303 = 0.461 per mnute.
= λNNow
= λN0; - λNt 9750 = λN0; 975 = λNt
⇒ N0 = 10Ntwe know that Nt = N0 = e-λt
= e-λt ⇒ = e-λ5 10-1 = e-5λ
Taking log on both sides,
1 - = - 5λ ×
λ =
× 2.303 = 0.461 per mnute. Create a free account to view solution
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