A radioactive substance decays at a rate proportional to the amount of substance present. If the half-life of the substance is 2 years, what fraction of the initial amount will remain after 6 years?
Correct: A
The decay of the substance follows the equation N = N0 * (1/2)^(t/T), where N is the amount of substance at time t, N0 is the initial amount, and T is the half-life. Substituting the given values, we get N = N0 * (1/2)^(6/2) = N0 * (1/2)^3 = N0 * 1/8, so the fraction of the initial amount remaining after 6 years is 1/8.