Which formula represents the inverse square law?

The inverse square law describes how the intensity of radiation or other point-source phenomena changes with distance. Specifically, as the distance from a source increases, the intensity decreases, and this decrease is proportional to the square of the distance from the source.

The correct formula, which states "Intensity 1 / Intensity 2 = Distance 2 squared / Distance 1 squared," captures this concept accurately. When the distance from the source is doubled, the intensity at that new distance is reduced to one fourth of its original value, reflecting the square relationship. Thus, the formula illustrates that the ratio of the intensities at two different distances can be calculated by taking the ratio of their respective distances squared.

By understanding that the intensity is inversely related to the square of the distance, one can predict how changes in distance affect the intensity of various types of radiation. This principle is fundamental in fields like radiology, where it helps to determine appropriate exposure levels and safety measures for both patients and healthcare providers.