The masses of two radioactive substances are same and their half-lives are 1 yr and 2 yr respectively. The ratio of their activities after 4 yr will be

Step-by-step solution

Let initial activity of both substances are same. aligned & R = R ₀ ( 1 2 )^ n = R ₀ ( 1 2 )^ t / t _ 1 / 2 R ₁ R ₂ &= ( 1 2 )^ 4 / 1 ( 1 2 )^ 4 / 2 = ( 1 2 )⁴ ( 1 2 )² = ( 1 2 )² R ₁ R ₂ &= 1 4 aligned