Question

Radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains?

(a) 1080

(b) 2430

(c) 3240

(d) 4860

This question was posed to me in an interview.

This interesting question is from Nucleus topic in division Nucleus of Physics – Class 12

Answer 1

The correct option is (a) 1080

The explanation: N = N0e^-(λ1 + λ2) t.

4 = e^(λ1 + λ2) t.

t = \(\frac {(2 \times 1620 \times 810)}{(2430)}\) = 1080 year.