Radiation Safety Practice Exam

Which type of radiation detection instrument utilizes the ionization principle?

1. Geiger counter

2. Thermal imager

3. Magnetic resonance imaging

4. Ultrasound device

The correct answer is: Geiger counter

The Geiger counter is a type of radiation detection instrument that operates on the principle of ionization. This instrument detects ionizing radiation, such as alpha and beta particles, or gamma rays, by measuring the electrical charge produced when radiation interacts with the gas within the Geiger-Müller tube. When ionizing radiation enters the tube, it ionizes the gas molecules, creating free electrons and positive ions. This ionization leads to the creation of an electrical current when a high voltage is applied across the tube. The Geiger counter counts these ionization events as individual pulses, which can be translated into a reading that indicates the level of radiation present in the environment. In contrast, the other options listed do not utilize the ionization principle for radiation detection. Thermal imagers detect radiation in the infrared spectrum based on temperature differences, magnetic resonance imaging relies on magnetic fields and radio waves for imaging, and ultrasound devices utilize sound waves to create images of structures within the body.