A substance has a half of 3mins. after 6mins. the count rate was observed to be 400. What was its count rate at zero time?
A
200
B
1200
C
1600
D
2400
Verified Correct Answer: C.
Physical Principles & Numerical Solution
Let the count rate at zero time be K
Count rate after 3mins, = \(\frac{K}{2}\)
Count rate after 6mins = \(\frac{K}{4}\)
but count after 6mins = 400 ( given )
Then = \(\frac{K}{4}\) = 400
K = 4 X 400 = 1600
∴ = count rate at zero time = 1600.
Source: Myschool Past Questions Archive (Record #28301)