Which type of radiation detection device is commonly used to monitor radiation levels?

The Geiger counter is widely used as a radiation detection device because it is specifically designed to measure ionizing radiation, which includes alpha particles, beta particles, and gamma rays. This device operates by using a Geiger-Müller tube that detects radiation through ionization. When radiation passes through the tube, it ionizes the gas within, leading to a measurable electrical pulse. This pulse is then translated into audible clicks or visual readings, allowing personnel to monitor radiation levels effectively and provide immediate feedback regarding exposure.

In contrast, the other options listed do not have the same capability or purpose as the Geiger counter. A fluorescent indicator is typically used for visual indications of certain conditions, not radiation levels. A digital multimeter is utilized for measuring electrical parameters such as voltage, current, and resistance, but it cannot detect ionizing radiation. A photoelectric cell is generally employed in applications involving light detection and does not serve any purpose in monitoring radiation exposure. Therefore, the Geiger counter stands out as the appropriate and commonly used device for monitoring radiation levels in industrial radiography settings.