According to the inverse square law, how does the intensity of radiation relate to distance from the source?

The intensity of radiation as described by the inverse square law demonstrates that as the distance from the source of radiation increases, the intensity decreases in proportion to the square of the distance. This means that if you double the distance from the source, the intensity becomes one-fourth of its original value.

The law is mathematically expressed as I = P / (4πr²), where I is the intensity, P is the power of the source, and r is the distance from the source. This relationship holds true because the energy emitted by the source spreads out over a larger area as the distance increases, leading to a decrease in intensity. Thus, the correct answer reflects this fundamental principle of how radiation spreads in space, significantly impacting various applications in radiology and radiation safety.