A radioactive sample with a half-life of `1` month has the label : 'Activity=
`2` microcurie on 1-8-1991'. What would be its avtivity two months earlier?

Options

A. 8 micro curie
B. 4 micro curie
C. 1 micro curie
D. 0.5 micro curie

Answer

A

Explanation

The half life = 1 month
`therefore` There are two half lives in 2 months or n=2
`therefore` From the ralation, `N/N_0 = (1/2)^2 = (1/4)`
`therefore` The activity is reduced to `1/4` of its original activity in 2 months.
`therefore` The activity of the sample before 2 months was `4xx2` = 8 microcurie.