How do we calculate the activity of a radioactive substance?

To calculate the activity of a radioactive substance, we use the equation A = λN, where A is the activity, λ is the decay constant, and N is the number of radioactive atoms.

Radioactivity is the process by which unstable atomic nuclei emit particles or electromagnetic radiation. The activity of a radioactive substance is the rate at which it emits radiation, measured in becquerels (Bq). One becquerel is equal to one decay per second.

The decay constant, λ, is a measure of how quickly a radioactive substance decays. It is defined as the probability of decay per unit time and is measured in reciprocal seconds (s^-1). The value of λ depends on the specific radioactive isotope.

The number of radioactive atoms, N, is the number of atoms in the sample that are capable of undergoing radioactive decay. It is measured in moles or number of atoms.

To calculate the activity of a radioactive substance, we simply multiply the decay constant by the number of radioactive atoms in the sample. This gives us the rate at which the substance is emitting radiation, or its activity.

It is important to note that the activity of a radioactive substance decreases over time as the number of radioactive atoms decreases due to decay. This is described by the exponential decay equation, N = N0e^-λt, where N0 is the initial number of radioactive atoms and t is the time elapsed. By using this equation, we can calculate the activity of a radioactive substance at any given time.

To understand the theory behind radioactive decay and the decay constant, you can refer to Radioactive Decay Law and Nature of Radioactive Decay. For a foundational understanding of radioactivity, including basic concepts and calculations, explore Radioactive Decay Basics.