A Geiger Muller counter is used to study the radioactive process. In the absence of radioactive substances `A`, it counts `3` disintegration per second (dps). At the start in the presence of `A`, it records `23` dps, and after `10 m` in `13 dps`,
i. What does it count after `20 m` in ?

Options

A. 8 dps, 10 min
B. 5 dps, 10 min
C. 5 dps, 20 min
D. 5 dps, 5 min

Answer

A

Explanation

In the absence of A, 3 dps is zero error, hence
Initial count=23- 3 = 20 dps
After 10 min=13-3=10 dps
After 20 min = 5 dps (recorded =5+3 = 8 dps)
(50% fall in 10 min, `T_(50)` = 10 min)