Final answer:
A medical assistant must wear a dosimeter when operating X-ray machines or other equipment that emits ionizing radiation, as it measures the radiation dose received.
Step-by-step explanation:
A medical assistant is required to wear a dosimeter when using equipment that emits ionizing radiation, such as X-ray machines. Dosimeters are personal radiation monitors that detect the amount of radiation by the discharge of a rechargeable internal capacitor. The amount of discharge is proportional to the exposure level to ionizing radiation, thereby giving a measurement of the dose received by the individual wearing the device.
These monitoring devices are critical for ensuring that medical personnel do not exceed the safe limits of radiation exposure. Among the devices used to measure radiation are Geiger counters, scintillators, and dosimeters. Film badges, another type of dosimeter, fog up when exposed to radiation, with the amount of fogging indicating the level of radiation exposure, although they are not as sensitive as electronic dosimeter systems that use crystals.