Final answer:
When analyzing an alpha track detector, the average radon level can be determined by comparing the exposure level of the film with a set of standard exposures. This can be done by developing the film and checking for exposure. Several factors can contribute to only a fraction of the emitted decays being observed by the detector.
Step-by-step explanation:
When analyzing an alpha track detector, the average radon level can be determined by comparing the exposure level of the film with a set of standard exposures. This can be done by developing the film and checking for exposure. By comparing the level of exposure on the film with the known activity of a radon source, the average radon level can be calculated.
For example, if the film exposed to a radon source labeled as having an activity of 1.0 μCi shows 1500 counts per minute, and the radon source was prepared 120 days before the measurement, the fraction of the decays observed by the detector can be calculated. This calculation can be done by comparing the observed counts per minute with the known activity of the radon source.
There are several factors that can contribute to only a fraction of the emitted decays being observed by the detector. These factors include the distance between the source and the detector, the shielding or absorption of the emitted radiation, and the efficiency of the detector in detecting and counting the emitted radiation.