Radioactivity is measured by

Radioactivity is measured by

GM Counter
Polarimeter
Calorimeter
Colorimeter
This question was previously asked in
UPSC NDA-2 – 2017
Radioactivity is the spontaneous emission of radiation (alpha, beta, gamma rays) from unstable atomic nuclei. A Geiger-Muller counter (GM Counter) is a widely used instrument specifically designed to detect and measure ionizing radiation, which is characteristic of radioactive decay. It works by detecting the ionization caused by radiation passing through a gas-filled tube.
– Radioactivity involves the emission of ionizing radiation.
– A GM Counter is an instrument that detects ionizing radiation.
A Polarimeter measures the rotation of polarized light by optical active substances. A Calorimeter measures heat flow or thermal energy. A Colorimeter measures the absorbance or transmission of light by a solution at specific wavelengths to determine concentration or color properties. None of these are used to measure radioactivity. Other instruments for measuring radioactivity include scintillation counters and semiconductor detectors.