Radiation Safety Practice Exam

How is nuclear (radioactive) decay defined?

1. An unstable nucleus releasing energy

2. A stable nucleus transforming into energy

3. A nucleus gaining neutrons over time

4. The absorption of radiation by a nucleus

The correct answer is: An unstable nucleus releasing energy

Nuclear (radioactive) decay is defined as the process by which an unstable atomic nucleus loses energy by emitting radiation. This often involves the release of particles or electromagnetic waves, which corresponds to the definition provided in the correct answer. During this process, the nucleus transitions from an unstable state to a more stable one, and energy is released as a result of this transformation. In the context of radioactivity, the most common forms of decay include alpha decay, beta decay, and gamma decay, each involving different types of emitted radiation. This emission is what signifies the instability of the nucleus and indicates it is undergoing decay. The other options do not accurately represent the concept of radioactive decay. A stable nucleus transforming into energy does not encompass the fundamental process of decay, as stable nuclei do not undergo such transformations. Similar misconceptions exist with the options regarding nuclei gaining neutrons or absorbing radiation, as these processes do not relate to the inherent characteristics of radioactive decay, which fundamentally involves the release of energy and particles from unstable nuclei.