|Uncharged radiations such as gamma ray photons must perform
a significant interaction in the detector before detection is possible.
Due to these types of radiation travelling large distances between
interactions, detectors are often less than 100% efficient.
The three main types of efficiency calibration are:
When calculating the efficiency of a detector at a specific time, the
activity of the calibration source must be confirmed.
The activity correction due to the source's half-life must be performed
using the decay equation.
[ Diagram here - advice needed for source ]