A freshly prepared radioactive source of half life 2 hours 30 minutes emits radiation which is 64 times the permissible safe level. The minimum time, after which it would be possible to work safely with source, will be _____ hours.

Step-by-step solution

Given here, T = 150 minutes, A 0 = 64 x , where, x is the safe limit. Using radioactive decay law relation, A = A 0 × 2 - t T , where, t is the minimum time in hours after which it would be possible to work safely with source. Putting the values, we have x = 64 x × 2 - t T ∴     t = 6   T = 6 × 2 . 5 = 15 hours