Question

A radioactive material $(t_{1/2}=30day)$ gets spilled over the floor of a room. If initial activity is ten times the permissible value, after how many day will it be safe to enter the room?

• A. 100
• B. 1000
• C. 300
• D. 10

Answer 1

The correct option is A 100

$t=\frac{2.303}{k}\log \frac{N_0}{N}$
$t_{1/2}=0.693/k$

$t=\frac{2.303\times 30}{0.693}\log \frac{10}{1}=100$