JEE Main · 2023 · 10 Apr 2023 · Shift 2 · Modern Physics

The half-life of a radioactive substance is T. The time taken, for disintegrating

\frac{7}{8}

th part of its original mass will be :

(A)3 T✓ Correct
(B)8 T
(C)T
(D)2 T

Answer: (A)

Solution

After each half-life period T, the remaining mass is halved. Starting with mass 1: after time T → 1/2 remains, after 2T → 1/4 remains, after 3T → 1/8 remains. If 1/8 remains, then 7/8 has disintegrated. Therefore, the time required is 3T.

JEE Main · 2023 · 10 Apr 2023 · Shift 2 · Single correct option

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