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:

Step-by-step solution

After 8 seconds count rate changes from A 1 = 1600 per second to A 2 = 100 per second. A 2 = A 1 16 = A 1 2 4 ∴ 8 s in 4 half life ⇒ 1 half life = 2   s t = 6 s is 3 half life. ∴ Count rate after 3 second A = A 1 2 3 = 1600 8 = 200