JEE Main2016PhysicsNuclear PhysicsActual
Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes , respectively. Initially, the samples have an equal number of nuclei. After 80 minutes , the ratio of decayed numbers of A and B nuclei will be:
Options
- A1   :   4
- B5   :   4
- C1   :   16
- D4   :   1
Correct answer
B. 5   :   4
Step-by-step solution
t = 80   m i n = 4   T A = 2 T B no. of nuclei of A decayed = N 0 - N 0 2 4 = 15 N 0 16 no. of nuclei of B decayed = N 0 - N 0 2 2 = 3 N 0 4 required ratio = 5 4