Question

The half life of radioactive element is `20 min`. The time interval between the stages of its `33%` and `67%` decay is
A. `40 min`
B. `20 min`
C. `30 min`
D. `25 min`

Answer 1

Correct Answer - B
Change in `67%` to `33%` is almost half the concentration change.
`67%underset("change")overset("Half")rarr 33.5 (~~ 33%)` ltbr. So time interval between the stages of its `33%` and `67%` decay is same as `t_(1//2) = 20 min`.