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

Options

A. 50 days
B. 30 days
C. 10 days
D. 100 days

Answer

D

Explanation

Let the permissible value of value of activity =A
Initial activity =10A
Given `t_(1//2)` =30 days `" " :.k=(ln2)/(30)`
Let after time t activity reduces from 10A to permissible value (A)
`t=(l)/(k) ln ((10A)/(A))=(30)/(ln(2))ln(10)=(30 xx 2.303)/(0.693)=100 ` days