question_answer

Using a nuclear counter the count rate of emitted particles from a radioactive source is measured. At  it was 1600 counts per second and  seconds it was 100 counts per second. The count rate observed, as counts per second, at  seconds is close to- [JEE Main 10-Jan-2019 Morning]

A) 200

B) 150  

C) 400

D) 360

Correct Answer: A

Solution :

[a]

at

second

In  sec number of half life’s = 3