Geiger-Müller counters are best used for which purpose?

• A. Measuring precise energy spectra of gamma rays.
• B. Monitoring tissue dose directly.
• C. Detecting presence and approximate strength of radiation; not ideal for precise dosimetry or high flux.
• D. Calibrating ionization chambers.

Answer: (C)

Geiger-Müller counters are best when you need to know that radiation is present and get a rough sense of its intensity, not when you require precise energy information or exact dose measurements. The GM tube produces a pulse for each ionizing event, but the pulse height isn’t related to the energy of the incoming radiation. That means you can detect that radiation exists and estimate how strong it is in a general sense, but you can’t determine its energy spectrum or convert counts into an accurate dose without additional calibration and assumptions about radiation type and geometry.

Because energy information is lost in the process, Geiger counters aren’t suitable for precise dosimetry, which relies on known energy response and tissue- or environment-specific calibration. They also can be limited at high flux due to dead time, where the detector misses subsequent events and the count rate no longer grows linearly with actual activity. For those reasons, the best use is detecting presence and approximate strength of radiation, rather than precise dosimetry or high-flux measurements.