Question

A half-life is the amount of time that it takes for a radioactive substance to decay to one half of its original quantity.

Suppose radioactive decay causes 300 grams of a substance to decrease to 300 × 2^–3 grams after 3 half-lives. Evaluate 300 × 2^–3 to determine how many grams of the substance are left.

Explain why the expression 300 × 2^–n can be used to find the amount of the substance that remains after n half-lives.

Answer 1

Since, 300 g of a substance is decrease to 300 × 2^–3 g after 3 half-lives.

So, we have to evaluate `300 xx 2^-3 = 300/8 = 37.5` g  ...[∵ 2³ = 8]