What principle do nuclear gauges use to measure density and moisture?

Nuclear gauges primarily rely on the interaction of radiation with matter to measure density and moisture. This technique utilizes radioactive isotopes, which emit gamma rays. When these gamma rays pass through a material, they interact with its atoms, causing a certain degree of absorption and scattering depending on the density and moisture content of that material.

As the radiation interacts with the material, the amount of radiation that is detected after passing through the material changes based on its density and moisture content. A denser material will attenuate more radiation compared to a less dense one, and moisture presence also affects the interaction. By measuring the intensity of the radiation before and after it passes through the material, the nuclear gauge can quantitatively assess both density and moisture levels.

This principle is fundamental in various applications, including construction, where accurate measurements of soil and concrete density and moisture content are essential for ensuring structural integrity. Other methods, such as those based on sound waves, light, or magnetic fields, do not provide the same level of precision or applicability in this context.