A radioactive element gets spilled over the floor of a room. Its half life period is 30 days. If the initial activity is ten times the permissibel value, after how many days will it be safe to enter the room?

Options

A. `-= 1000` days
B. `-= 300` days
C. `-= 10` days
D. `-= 100` days

Answer

`(d)`

Explanation

It will be safe to enter in the room when activity gets reduced by 10 times, i.e., when `N = N_(0)//10`
` :' (N)/(N_(0)) = ((1)/(2))^(n)`
or `(1)/(10) = ((1)/(2))^(n)`
or `10 = 2^(n)`
`log 10 = n log 2`
`n = (1)/(0.301) = 3.32`
`t = n xx t_(1//2)`
`= 3.32xx30 = 99.6` days