A radioactive substance has a half-life of four months. Three-fourth of substance

A radioactive substance has a half-life of four months. Three-fourth of substance will decay in

Options

(a) 3 months
(b) 4 months
(c) 8 months
(d) 12 months

Correct Answer:

8 months

Explanation:

Substance left undecayed N = N₀ – (3 / 4) N₀ = (1 /4) N₀

N / N₀ = (1 / 2)ⁿ

where n = number of half lives

.·. 1 / 4 = (1 / 2)ⁿ (or), n = 2 n = t / T₁/₂ t = nT₁/₂ = 2 × 4 = 8 months.

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