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The radioactive isotope, tritium (³₁H) has a half-life of 12.3 years. If the initial amount of tritium is 32 mg, how many milligrams of it would remain after 49.2 years?

1. 8 mg
2. 1 mg
3. 2 mg
4. 4 mg

Correct answer: 4 mg

Solution

The half-life formula is used: N = N₀(1/2)^(t/t₁/₂). Here, t = 49.2 years, t₁/₂ = 12.3 years, and N₀ = 32 mg. Substituting, N = 32(1/2)^(49.2/12.3) = 32(1/2)^4 = 32 × 1/16 = 2 mg.

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