Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes
PHYSICS · Single correct · A Level · Physics · Nuclear physics · Nuclear physics
Problem
Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, what is the ratio of the number of decayed nuclei of A to B?
(1) 1 : 4
(2) 5 : 4
(3) 1 : 16
(4) 4 : 1