If two isotopic sources have the same strength but different specific activity values, what can be determined about the source with higher specific activity?

The source with higher specific activity indicates that it has a greater amount of radioactivity per unit mass or volume compared to the source with the same strength but lower specific activity. Specific activity is defined as the activity (amount of radioactive decay) per unit of mass of the radioactive material. Therefore, if one source has a higher specific activity, it contains less mass of the radioactive material while maintaining the same level of radioactivity (strength).

This higher specific activity often corresponds to a source that is physically smaller because it can achieve the same radioactivity with a lesser quantity of material. In practice, this means that a radioactive material with high specific activity is likely to be more concentrated, containing a higher number of radioactive atoms per unit of volume. Hence, the determination that it is of smaller physical size aligns with the concept of specific activity.

Additionally, older sources generally have lower specific activity due to radioactive decay, which reduces the quantity of active radionuclides available, thus typically leading to lower activity for a given mass of material. The other choices do not accurately reflect the relationship between specific activity and the physical characteristics or age of the sources.