ARRT Practice Exam 2025 – Complete Study Guide for Radiologic Technologists

The concept that governs the relationship between x-ray beam intensity and the distance from the source to the image receptor is the Inverse Square Law. This law states that the intensity of a radiation source, like an x-ray beam, decreases with the square of the distance from the source.

In practical terms, if you double the distance from the x-ray tube to the image receptor, the intensity of the x-ray beam reaching the receptor is reduced to one-fourth of its original value. Conversely, decreasing the distance will increase the intensity, highlighting how sensitive x-ray imaging techniques are to changes in this distance. Understanding this principle is crucial for radiologic technologists, as it directly influences image quality and patient exposure to radiation.

The other concepts listed, such as Ohm's Law, which pertains to electrical circuits, the Hertzsprung-Russell Diagram related to stars and their luminosity, and Kirchhoff's Law, dealing with thermal radiation and emissivity, do not pertain to the behavior of radiation intensity with distance in the context of x-ray imaging.