A radioactive sample has an activity R.For which of the following changes would the activity remain unchanged?
A)The number of radioactive nuclei in the sample is doubled.
B)The half-life of the radioactive nuclei is doubled.
C)The decay constant is doubled.
D)A time period equal to two half-lives is allowed to elapse.
E)All of the above changes result in a change in the activity.

Question

A radioactive sample has an activity R.For which of the following changes would the activity remain unchanged?​
A)​The number of radioactive nuclei in the sample is doubled.
B)​The half-life of the radioactive nuclei is doubled.
C)​The decay constant is doubled.
D)​A time period equal to two half-lives is allowed to elapse.
E)​All of the above changes result in a change in the activity.

Quizplus · Accepted Answer

The activity of a radioactive sample is directly proportional to the number of radioactive nuclei present and the decay constant. Doubling the number of nuclei (A), doubling the half-life (which inversely affects the decay constant, B), doubling the decay constant directly (C), or allowing time to elapse (which reduces the number of radioactive nuclei, D) would all change the activity. Therefore, none of the changes listed would leave the activity unchanged.

A Radioactive Sample Has an Activity R