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 permissible value, after how many days will it be safe to enter the room ?

Options

A. 300 days
B. 10 days
C. 100 days
D. 1000 days.

Answer

C

Explanation

Let the permissible activity limit be x, then initial activity would be 10x
`lamda=(0.693)/(30"days")`
`t=(2.303)/(lamda)log"([A]_(0))/([A])`
`=(2.303xx30)/(0.693)"log"(10x)/(x)`
`=99.7"days"~~100` days.