Question

The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life of 30 minutes decreases to 5 second^-1 after 2 hours. The initial count rate was

(a) 80 second^-1

(b) 625 second^-1

(c) 20 second^-1

(d) 25 second^-1

Answer 1

The correct option is (a) 80 second^-1.

Explanation:

Half-life time = 30 minutes; Rate of decrease (N) = 5 per second and total time = 2 hours = 120 minutes. Relation for initial and final count