Final answer:
The three types of photoelectric intrusion sensors commonly encountered are Geiger counters, scintillators, and dosimeters, all of which measure radiation through different means but are not primarily designed for intrusion detection.
Step-by-step explanation:
The student is asking about photoelectric intrusion sensors, which are devices that detect unauthorized entry or movement by using the photoelectric effect. The three commonly encountered types of these sensors in security systems are: Geiger counters, scintillators, and dosimeters. These devices measure radiation, which is a related but different concept from photoelectric intrusion detection. However, the principles of photon detection are similar.
Each type of sensor works by detecting radiation through different means: a Geiger counter detects ionizing radiation with a tube that is sensitive to this radiation, a scintillator uses materials that emit light when exposed to ionizing radiation, and dosimeters measure an individual's exposure to radiation over time. These technologies are also applied in other fields, such as biomedical imaging systems and solid-state radiation detectors in semiconductors, to directly convert incident radiation into electrical current.