The half life of a radioactive substance is 20 minutes. The approximate time interval (t₂ - t₁) between the time t₂ when 2/3 of it had decayed and time t₁ when 1/3 of it had decayed is: (a) 14 min (b) 20 min (c) 28 min (d) 7 min

Answer: (b). At t₁, 2/3 remains; at t₂, 1/3 remains. The remaining amount halves, so t₂ - t₁ = T = 20 min. So the answer is (b) 20 min.

The half life of a radioactive substance is 20 minutes. The… | JEE Main 2011 (AIEEE)

Q102JEE Main 2011 · AIEEEMedium

Law of Radioactive Decay

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 it had decayed and time $t_1$ when $\frac{1}{3}$ of it had decayed is:

Show answer and solution

Answer: (b)

At $t_1$ , $\frac{2}{3}$ remains; at $t_2$ , $\frac{1}{3}$ remains.
The remaining amount halves, so $t_2 - t_1 = T = 20$ min.
So the answer is (b) 20 min.

Report a mistake

Law of Radioactive Decay question from JEE Main 2011 (AIEEE)

More questions on Law of Radioactive Decay