JEE Main2011PhysicsNuclear PhysicsActual
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 has decayed and time t₁ and 1 3 of it had decayed is :
Options
- A14 ~min
- B20 ~min
- C28 ~min
- D7 ~min
Correct answer
B. 20 ~min
Step-by-step solution
t _ 1 2 =20 minutes N = N ₀ e ^ - t ₂ t ₁= 3 2 3 ~N ₀= N ₀ e ^ - t ₂ t ₁= 1 3 2 3 ~N ₀= N ₀ e ^ - t₂ t ₂= 1 3 2 t ₂- t ₁= 1 [ 3 2 - 3 ]= 1 [ 1 2 ]= 0.693 =20