JEE Main 2019 Physics question
Using a nuclear counter the count rate of emitted particles from a radioactive source is measured. At t = 0 it was 1600 counts per second and t = 8 seconds it was 100 counts per second. The count rate observed, as counts per second, at t = 6 seconds is close to:
Answer: (A)
Solution
1600 → 100 is four half-lives in 8 s, so T = 2 s; at 6 s: 1600/8 = 200.