An accident in a nuclear labora tory resulted in deposition of a certa...
To find the minimum number of days after which the laboratory can be considered safe for use, we need to determine the time it takes for the radioactive material to decay to a level that is permissible for safe operation.
Let's assume the initial amount of radioactive material is 'A' and the permissible level is 'P'. It is given that the radiation is 64 times more than the permissible level, so we can write:
A/P = 64
The half-life of the radioactive material is given as 18 days. This means that after every 18 days, the amount of radioactive material is reduced to half.
Now, let's consider the radioactive material after 'n' half-lives. The amount of radioactive material remaining after 'n' half-lives can be given as:
A * (1/2)^n
We want to find the minimum number of days, 'D', after which the radiation is reduced to the permissible level. So, we can write:
A * (1/2)^D = P
Now, substituting the value of A/P from the first equation, we get:
64 * (1/2)^D = 1
Simplifying the equation, we have:
2^6 * (1/2)^D = 1
2^(6-D) = 1
The only possible value of D that satisfies the equation is 6. Therefore, the minimum number of days after which the laboratory can be considered safe for use is 6 * 18 = 108 days.
So, the correct answer is option 'C' - 108 days.