Radon, 222Rn86 is a radioactive gas that can be trapped in the concrete in the basement of a house.?

Question

It emits α and γ radiation with a half-life of 3.8 days. If present in high concentration, it is a significant health hazard. Suppose that a health inspector finds an activity level of 2 x 105 Bq in the basement.

(i)What will the activity after 7 days?
(ii)What will the activity after 14 days?
(iii)How long must the residents of the house wait until the activity has decreased to 1 Bq?

Answer 1

R=Ro e^(-.693t/T) where t is elapsed time and T is half life
so i) =2x10^5 e^(-.693x7/3.8)
ii) pug in 14 days instead of 7
iii) solve for t with R=1Bq

Answer 2

The time period will be depends upon the quantity of the gas in the trap