Question

# The activity of a radioactive sample is measured as 9750 count/min at t = 0 and 975 count/min at t = 5 min.The decay constant is nearly

A
0.922 min1
B
0.691 min1
C
0.461 min1
D
0.230 min1
Solution
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#### Initial activity of the sample Ro=9750 count/minActivity after t=5 min, R=975 count/minUsing First order decay, R=Roe−λt∴ 975=9750e−5λOr −ln10=−5λOr 2.303=5λ⟹ λ=0.461 min−1

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