The decay constant of 238U is 4.9 × 10–18 s–1.
(a) What is the average-life of 238U?
(b) What is the half-life of 238U?
(c) By what factor does the activity of a 238U sample decrease in 9 × 109 years?
Given,
The decay constant of 238U is 4.9 × 10–18 s–1
a) Average life
b) Half life
c) 9 × 109 years = 2 half-lives(approximately)
We know
where A= Activity of the substance
A0 = Initial activity
N = number of half lives
N = 2, in this case.
So it is evident that the sample activity will decrease by a factor of 4