The half life of a radioactive substance is 20 minutes. The approximate time interval (t2-t1) between the time t2 when (2/3) of its has decayed and time t1 when (1/3) of its had decayed is

Question

The half life of a radioactive substance is 20 minutes. The approximate time interval (t2-t1) between the time t2 when (2/3) of its has decayed and time t1 when (1/3) of its had decayed is (A) 28 min (B) 7 min (C) 14 min (D) 20 min

Tardigrade Admin · Accepted Answer

At t=t2, N2=(N/3) (Left) t=t1, N1=(2 N/3) ⇒ t2-t1= half life =20 min

Q. The half life of a radioactive substance is 20 minutes. The approximate time interval $(t_{2} - t_{1})$ between the time $t_{2}$ when $\frac{2}{3}$ of its has decayed and time $t_{1}$ when $\frac{1}{3}$ of its had decayed is

$28 min$

$7 min$

$14 min$

$20 min$

At $t = t_{2}, N_{2} = \frac{N}{3}$ (Left)
$t = t_{1}, N_{1} = \frac{2 N}{3}$
$\Rightarrow t_{2} - t_{1} =$ half life $= 20 min$

Q. The half life of a radioactive substance is 20 minutes. The approximate time interval (t2​−t1​) between the time t2​ when 32​ of its has decayed and time t1​ when 31​ of its had decayed is

28min

7min

14min

20min