What instrument is used to measure radiation and what principle does it rely on?

• A. Geiger-Muller counter; detects ionizing radiation via gas ionization to produce clicks.
• B. Geiger-Muller counter; detects non-ionizing radiation via heat.
• C. Geiger-Muller counter; measures chemical hazards.
• D. Geiger-Muller counter; detects temperature changes.

Answer: (A)

Detecting ionizing radiation with a Geiger-Muller counter relies on the gas ionization principle. When ionizing radiation enters the Geiger-Muller tube filled with inert gas and a high voltage is applied, each radiation event ionizes the gas atoms, freeing electrons and creating a cascade of charge that yields a short electrical pulse. The circuitry counts these pulses, producing a click or a readout of radiation level. This instrument measures how often events occur (counts per unit time), not the energy of the radiation. It isn’t designed to detect non-ionizing radiation, temperature changes, or chemical hazards, which is why those descriptions don’t fit.