The count rate of a geiger Muller counter for radiation of a radioactive material of half life of 30 minutes decreases to 5 /s after 2 hours. The initial count rate was.?
1-80/s 2-625/s
3-20/s 4-25/s
N/N0 = (1/2)n . Given that half life = 30 minutes .
Then, number of half lives in 2 hours or, 120 minutes is, n = 120/30 = 4 = 4 .
Now, N/N0 = (1/2)4 = 1/16 ; N0 = N * 16 = 5 * 16 = 80 second-1 .
Then, number of half lives in 2 hours or, 120 minutes is, n = 120/30 = 4 = 4 .
Now, N/N0 = (1/2)4 = 1/16 ; N0 = N * 16 = 5 * 16 = 80 second-1 .