Question

1.
Out of 10 mg of a radio active sample, 1.25 mg
remains undecayed after 6 hours. The mean life of
the sample in hours is
A. 0.693
B. 2/0.693
C. 4/0.693
D. 0.693/4​

Answer 1

Explanation:

have, N = N0/2n so that 1.25 = 10/2n, from which 2n = 8 and n = 3. So, 3 half life periods is 6 hours so that the half life of the sample is 2 hours.

Mean life, T = 1/λ = Thalf /0.693 = 2/0.693 [Option (b)].

Let us consider one more question involving radio activity: