The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40 % decay and 85 % decay of the same radioactive substance is :-

Question

The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40 % decay and 85 % decay of the same radioactive substance is :- (A) 45 (B) 60 (C) 15 (D) 30

Tardigrade Admin · Accepted Answer

decay 40 % arrow 85 % Remaining 60 % arrow 15 % 60 % oversett1 / 2 arrow 30 % oversett1 / 2 arrow 15 % ∴ t=2t1 / 2=60min

Q. The half-life of a radioactive substance is $30$ minutes. The time (in minutes) taken between $40%$ decay and $85%$ decay of the same radioactive substance is :-

$45$

$60$

$15$

$30$

decay $40% \to 85%$
Remaining $60% \to 15%$
$60% \to t_{1/2} 30% \to t_{1/2} 15%$
$∴ t = 2 t^{1/2} = 60 min$

Q. The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40% decay and 85% decay of the same radioactive substance is :-

45

60

15

30